Conversion 1.5+ : Java Glossary

2008-03-25 by Roedy Green ©1996-2008 Canadian Mind Products
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Conversion 1.5+

This table will help you convert from any of the basic data types to any other in Java 1.5 or later. This table is also available in a Java 1.4 or earlier version. Please report any errors or omissions. This table is also available as an amanuensis Applet or as a download with source code.

Conversion Amanuensis	StringBuffers & StringBuilders
Conversion Matrix for JDK 1.4-	Rounding
Conversion Matrix for JDK 1.5+	Left Zeros
Primitives	Formatted Output
Basic Types	Reading Numeric Data
Truncation	StreamTokenizer
byte[] ⇔ String	StringTokenizer
char[] ⇔ String	Binary
Hexadecimal	Links

JDK 1.5+ Convert To
From	to: boolean t	to: /signed/ byte b	to: /unsigned/ byte u	to: short s	to: char c	to: int i	to: long n	to: float f	to: double d	to: String g	to: Boolean tt	to: /signed/ Byte bb	to: /unsigned/ Byte uu	to: Short ss	to: Character cc	to: Integer ii	to: Long nn	to: Float ff	to: Double dd	From
boolean t	--------	// to /signed/ byte b from boolean t b = (byte)(t?1:0);	// to /unsigned/ byte u from boolean t u = (byte)(t?1:0);	// to short s from boolean t s = (short)(t?1:0);	// to char c from boolean t // to get '0' and '1' c = (char)(t?'1':'0'); // or to get Unicode value 0 or 1 c = (char)(t?1:0);	// to int i from boolean t i = t?1:0;	// to long n from boolean t n = t?1:0;	// to float f from boolean t f = t?1:0;	// to double d from boolean t d = t?1:0;	// to String g from boolean t g = String.valueOf(t);	// to Boolean tt from boolean t // no conversion necessary in Java 1.5+	// to /signed/ Byte bb from boolean t bb = new Byte((byte)(t?1:0));	// to /unsigned/ Byte uu from boolean t uu = new Byte((byte)(t?1:0));	// to Short ss from boolean t ss = new Short((short)(t?1:0));	// to Character cc from boolean t // to get '0' or '1' cc = new Character((char)(t?'1':'0')); // or to get Unicode 0 or 1 cc = new Character((char)(t?0:1));	// to Integer ii from boolean t // best JDK 1.5+ ii = Integer.valueOf(t?1:0); // or JDK 1.4- ii = new Integer(t?1:0);	// to Long nn from boolean t // best JDK 1.5+ nn = Long.valueOf(t?1:0); // or JDK 1.4- nn = new Long(t?1:0);	// to Float ff from boolean t ff = new Float(t?1:0);	// to Double dd from boolean t dd = new Double(t?1:0);	boolean t
/signed/ byte b	// to boolean t from /signed/ byte b t = b != 0;	--------	// to /unsigned/ byte u from /signed/ byte b // no conversion necessary in Java 1.5+	// to short s from /signed/ byte b // no conversion necessary in Java 1.5+	// to char c from /signed/ byte b // no conversion necessary in Java 1.5+	// to int i from /signed/ byte b // no conversion necessary in Java 1.5+	// to long n from /signed/ byte b // no conversion necessary in Java 1.5+	// to float f from /signed/ byte b // no conversion necessary in Java 1.5+	// to double d from /signed/ byte b // no conversion necessary in Java 1.5+	// to String g from /signed/ byte b // best for readability g = Integer.toString(b); // best for maintainability g = String.valueOf(b); // or g = Integer.toString(b, 7 /* radix */); // or g = Integer.toBinaryString(b); // or g = Integer.toOctalString(b); // or g = Integer.toHexString(b); // or kludgy and slow on unoptimised Javas g = "" + b;	// to Boolean tt from /signed/ byte b tt = (b != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from /signed/ byte b // no conversion necessary in Java 1.5+	// to /unsigned/ Byte uu from /signed/ byte b // no conversion necessary in Java 1.5+	// to Short ss from /signed/ byte b // no conversion necessary in Java 1.5+	// to Character cc from /signed/ byte b // no conversion necessary in Java 1.5+	// to Integer ii from /signed/ byte b // no conversion necessary in Java 1.5+	// to Long nn from /signed/ byte b // no conversion necessary in Java 1.5+	// to Float ff from /signed/ byte b // no conversion necessary in Java 1.5+	// to Double dd from /signed/ byte b // no conversion necessary in Java 1.5+	/signed/ byte b
/unsigned/ byte u	// to boolean t from /unsigned/ byte u t = u != 0;	// to /signed/ byte b from /unsigned/ byte u // no conversion necessary in Java 1.5+	--------	// to short s from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to char c from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to int i from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to long n from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to float f from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to double d from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to String g from /unsigned/ byte u // best for readability g = Integer.toString(u & 0xff); // best for maintainability g = String.valueOf(u & 0xff); // or g = Integer.toString(u & 0xff, 7 /* radix */); // or g = Integer.toBinaryString(u & 0xff); // or g = Integer.toOctalString(u & 0xff); // or g = Integer.toHexString(u & 0xff); // or kludgy and possibly slow g = "" + (u & 0xff);	// to Boolean tt from /unsigned/ byte u tt = (u != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to /unsigned/ Byte uu from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to Short ss from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to Character cc from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to Integer ii from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to Long nn from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to Float ff from /unsigned/ byte u // no conversion necessary in Java 1.5+	// to Double dd from /unsigned/ byte u // no conversion necessary in Java 1.5+	/unsigned/ byte u
short s	// to boolean t from short s t = s != 0;	// to /signed/ byte b from short s b = (byte)s;	// to /unsigned/ byte u from short s u = (byte)s;	--------	// to char c from short s // no conversion necessary in Java 1.5+	// to int i from short s // no conversion necessary in Java 1.5+	// to long n from short s // no conversion necessary in Java 1.5+	// to float f from short s // no conversion necessary in Java 1.5+	// to double d from short s // no conversion necessary in Java 1.5+	// to String g from short s // best for readability g = Integer.toString(s); // best for maintainability g = String.valueOf(s); // or g = Integer.toString(s, 7 /* radix */); // or g = Integer.toBinaryString(s); // or g = Integer.toOctalString(s); // or g = Integer.toHexString(s); // or kludgy and possibly slow g = "" + s;	// to Boolean tt from short s tt = (s != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from short s bb = new Byte((byte)s);	// to /unsigned/ Byte uu from short s uu = new Byte((byte)s);	// to Short ss from short s // no conversion necessary in Java 1.5+	// to Character cc from short s // no conversion necessary in Java 1.5+	// to Integer ii from short s // no conversion necessary in Java 1.5+	// to Long nn from short s // no conversion necessary in Java 1.5+	// to Float ff from short s // no conversion necessary in Java 1.5+	// to Double dd from short s // no conversion necessary in Java 1.5+	short s
char c	// to boolean t from char c // to convert '0' or '1' t = c != '0'; // to convert Unicode 0 or 1 t = c != 0;	// to /signed/ byte b from char c // international b = (byte)Character.digit(c, 10 /* radix */); // fastest '9' -> 9 b = (byte)(c - '0'); // or to get Unicode value b = (byte)c;	// to /unsigned/ byte u from char c // international u = (byte)Character.digit(c, 10 /* radix */); // fastest '9' -> 9 u = (byte)(c - '0'); // or to get Unicode value u = (byte)c;	// to short s from char c // no conversion necessary in Java 1.5+	--------	// to int i from char c // no conversion necessary in Java 1.5+	// to long n from char c // no conversion necessary in Java 1.5+	// to float f from char c // no conversion necessary in Java 1.5+	// to double d from char c // no conversion necessary in Java 1.5+	// to String g from char c g = String.valueOf(c);	// to Boolean tt from char c // for '0' or '1' tt = (c != '0') ? Boolean.TRUE : Boolean.FALSE; // or for Unicode 0 or 1 tt = (c != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from char c bb = new Byte((byte)c);	// to /unsigned/ Byte uu from char c uu = new Byte((byte)c);	// to Short ss from char c // no conversion necessary in Java 1.5+	// to Character cc from char c // no conversion necessary in Java 1.5+	// to Integer ii from char c // no conversion necessary in Java 1.5+	// to Long nn from char c // no conversion necessary in Java 1.5+	// to Float ff from char c // no conversion necessary in Java 1.5+	// to Double dd from char c // no conversion necessary in Java 1.5+	char c
int i	// to boolean t from int i t = i != 0;	// to /signed/ byte b from int i b = (byte)i;	// to /unsigned/ byte u from int i u = (byte)i;	// to short s from int i s = (short)i;	// to char c from int i // 9 -> '9' c = (char)(i + '0'); // or to get Unicode value c = (char)i;	--------	// to long n from int i // no conversion necessary in Java 1.5+	// to float f from int i // no conversion necessary in Java 1.5+	// to double d from int i // no conversion necessary in Java 1.5+	// to String g from int i // best for readability g = Integer.toString(i); // best for maintainability g = String.valueOf(i); // or g = Integer.toString(i, 7 /* radix */); // or g = Integer.toBinaryString(i); // or g = Integer.toOctalString(i); // or g = Integer.toHexString(i); // or kludgy and possibly slow g = "" + i;	// to Boolean tt from int i tt = (i != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from int i bb = new Byte((byte)i);	// to /unsigned/ Byte uu from int i uu = new Byte((byte)i);	// to Short ss from int i ss = new Short((short)i);	// to Character cc from int i // 9 -> '9' cc = new Character((char)(i + '0')); // or to get Unicode value cc = new Character((char)i);	// to Integer ii from int i // no conversion necessary in Java 1.5+	// to Long nn from int i // no conversion necessary in Java 1.5+	// to Float ff from int i // no conversion necessary in Java 1.5+	// to Double dd from int i // no conversion necessary in Java 1.5+	int i
long n	// to boolean t from long n t = n != 0;	// to /signed/ byte b from long n b = (byte)n;	// to /unsigned/ byte u from long n u = (byte)n;	// to short s from long n s = (short)n;	// to char c from long n // 9 -> '9' c = (char)(n + '0'); // or to get Unicode value c = (char)n;	// to int i from long n i = (int)n;	--------	// to float f from long n // no conversion necessary in Java 1.5+	// to double d from long n // no conversion necessary in Java 1.5+	// to String g from long n // best for readability g = Long.toString(n); // best for maintainability g = String.valueOf(n); // or g = Long.toString(n, 7 /* radix */); // or g = Long.toBinaryString(n); // or g = Long.toOctalString(n); // or g = Long.toHexString(n); // or kludgy and possibly slow g = "" + n;	// to Boolean tt from long n tt = (n != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from long n bb = new Byte((byte)n);	// to /unsigned/ Byte uu from long n uu = new Byte((byte)n);	// to Short ss from long n ss = new Short((short)n);	// to Character cc from long n // 9 -> '9' cc = new Character((char)(n + '0')); // or to get Unicode value cc = new Character((char)n);	// to Integer ii from long n // best JDK 1.5+ ii = Integer.valueOf((int)n); // or JDK 1.4- ii = new Integer((int)n);	// to Long nn from long n // no conversion necessary in Java 1.5+	// to Float ff from long n // no conversion necessary in Java 1.5+	// to Double dd from long n // no conversion necessary in Java 1.5+	long n
float f	// to boolean t from float f t = f != 0;	// to /signed/ byte b from float f b = (byte)f;	// to /unsigned/ byte u from float f u = (byte)f;	// to short s from float f s = (short)f;	// to char c from float f c = (char)f;	// to int i from float f // best i = (int)f; // or i = Math.round(f); // or i = (int)Math.ceil(f); // or i = (int)Math.floor(f); // to see the IEEE bits inside a float i = Float.floatToIntBits(f);	// to long n from float f // best n = (long)f; // or n = Math.round(f); // or n = (long)Math.ceil(f); // or n = (long)Math.floor(f);	--------	// to double d from float f // no conversion necessary in Java 1.5+	// to String g from float f // 2 decimal places, rounded, locale-sensitive. java.text.DecimalFormat df2 = new java.text.DecimalFormat("###,##0.00"); g = df2.format(f); // or exponential scientific format, locale-sensitive. java.text.DecimalFormat de = new java.text.DecimalFormat("0.000000E00"); g = de.format(f); // or best for readability, no loss of precision, locale-insensitive g = Float.toString(f); // or best for maintainability, no loss of precision, locale-insensitive g = String.valueOf(f);	// to Boolean tt from float f tt = (f != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from float f bb = new Byte((byte)f);	// to /unsigned/ Byte uu from float f uu = new Byte((byte)f);	// to Short ss from float f ss = new Short((short)f);	// to Character cc from float f cc = new Character((char)f);	// to Integer ii from float f // best JDK 1.5+ ii = Integer.valueOf((int)f); // or JDK 1.4- ii = new Integer((int)f);	// to Long nn from float f // best JDK 1.5+ nn = Long.valueOf((long)f); // or JDK 1.4- nn = new Long((long)f);	// to Float ff from float f // no conversion necessary in Java 1.5+	// to Double dd from float f // no conversion necessary in Java 1.5+	float f
double d	// to boolean t from double d t = d != 0;	// to /signed/ byte b from double d b = (byte)d;	// to /unsigned/ byte u from double d u = (byte)d;	// to short s from double d s = (short)d;	// to char c from double d c = (char)d;	// to int i from double d // best i = (int)d; // or i = (int)Math.round(d); // or i = (int)Math.ceil(d); // or i = (int)Math.floor(d);	// to long n from double d // best n = (long)d; // or n = Math.round(d); // or n = (long)Math.ceil(d); // or n = (long)Math.floor(d); // to see the IEEE bits inside a double n = Double.doubleToLongBits(d);	// to float f from double d f = (float)d;	--------	// to String g from double d // 2 decimal places, rounded, locale-sensitive. java.text.DecimalFormat df2 = new java.text.DecimalFormat("###,##0.00"); g = df2.format(d); // or exponential scientific format, locale-sensitive. java.text.DecimalFormat de = new java.text.DecimalFormat("0.0000000000E00"); g = de.format(d); // or best for readability, no loss of precision, locale-insensitive g = Double.toString(d); // or best for maintainability, no loss of precision, locale-insensitive g = String.valueOf(d);	// to Boolean tt from double d tt = (d != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from double d bb = new Byte((byte)d);	// to /unsigned/ Byte uu from double d uu = new Byte((byte)d);	// to Short ss from double d ss = new Short((short)d);	// to Character cc from double d cc = new Character((char)d);	// to Integer ii from double d // best JDK 1.5+ ii = Integer.valueOf((int)d); // or JDK 1.4- ii = new Integer((int)d);	// to Long nn from double d // best JDK 1.5+ nn = Long.valueOf((long)d); // or JDK 1.4- nn = new Long((long)d);	// to Float ff from double d ff = new Float(d);	// to Double dd from double d // no conversion necessary in Java 1.5+	double d
String g	// to boolean t from String g t = new Boolean(g.trim()).booleanValue(); // or t = g.trim().equalsIgnoreCase("true");	// to /signed/ byte b from String g try { // best b = (byte)Integer.parseInt(g.trim()); // or b = (byte)Integer.parseInt(g.trim(), 16 /* radix /); } catch (NumberFormatException e){/ ... */}	// to /unsigned/ byte u from String g try { // best u = (byte)Integer.parseInt(g.trim()); // or u = (byte)Integer.parseInt(g.trim(), 16 /* radix /); } catch (NumberFormatException e){/ ... */}	// to short s from String g try { // best s = (short)Integer.parseInt(g.trim()); // or s = (short)Integer.parseInt(g.trim(), 16 /* radix /); } catch (NumberFormatException e){/ ... */}	// to char c from String g try { // "9" -> '9' c = g.charAt(0 /* position /); // or to get Unicode value c = (char)Integer.parseInt(g.trim()); // or to get Unicode hex value c = (char)Integer.parseInt(g.trim(), 16 / radix /); } catch (NumberFormatException e){/ ... */}	// to int i from String g try { // best i = Integer.parseInt(g.trim()); // or i = Integer.parseInt(g.trim(), 16 /* radix /); } catch (NumberFormatException e){/ ... */}	// to long n from String g try { n = Long.parseLong(g.trim()); } catch (NumberFormatException e){/* ... */}	// to float f from String g try { // best locale-insensitive f = Float.parseFloat(g.trim()); // or locale-insensitive f = Float.valueOf(g.trim()).floatValue(); } catch (NumberFormatException e){/* ... */}	// to double d from String g try { // best, locale-insensitive d = Double.parseDouble(g.trim()); // or locale-insensitive d = Double.valueOf(g.trim()).doubleValue(); } catch (NumberFormatException e){/* ... */}	--------	// to Boolean tt from String g // best tt = new Boolean(g.trim()); // or tt = Boolean.valueOf(g.trim());	// to /signed/ Byte bb from String g try { // best bb = new Byte(Byte.parseByte(g.trim())); // or bb = new Byte(Byte.parseByte(g.trim(), 16 /* radix /)); // or bb = new Byte((byte)g.charAt(0 / position /)); } catch (NumberFormatException e){/ ... */}	// to /unsigned/ Byte uu from String g try { // best uu = new Byte(Byte.parseByte(g.trim())); // or uu = new Byte(Byte.parseByte(g.trim(), 16 /* radix /)); // or uu = new Byte((byte)g.charAt(0 / position /)); } catch (NumberFormatException e){/ ... */}	// to Short ss from String g try { // best ss = new Short(Short.parseShort(g.trim())); // or ss = new Short(Short.parseShort(g.trim(), 16 /* radix /)); // or ss = new Short((short)g.charAt(0 / position /)); } catch (NumberFormatException e){/ ... */}	// to Character cc from String g try { // "9" -> '9' cc = new Character(g.charAt(0 /* position /)); // or to get Unicode value cc = new Character((char)Integer.parseInt(g.trim())); // or to get Unicode hex value cc = new Character((char)Integer.parseInt(g.trim(), 16 / radix /)); } catch (NumberFormatException e){/ ... */}	// to Integer ii from String g try { // best, caches ii = Integer.valueOf(g.trim()); // or ii = new Integer(g.trim()); } catch (NumberFormatException e){/* ... */}	// to Long nn from String g try { // best, caches nn = Long.valueOf(g.trim()); // or nn = new Long(g.trim()); } catch (NumberFormatException e){/* ... */}	// to Float ff from String g try { // best, locale-insensitive. ff = new Float(g.trim()); // or locale-insensitive ff = Float.valueOf(g.trim()); } catch (NumberFormatException e){/* ... */}	// to Double dd from String g try { // best, locale-insensitive/ dd = new Double(g); // or locale-insensitive dd = Double.valueOf(g); } catch (NumberFormatException e){/ ... */}	String g
Boolean tt	// to boolean t from Boolean tt // no conversion necessary in Java 1.5+	// to /signed/ byte b from Boolean tt b = (byte)(tt.booleanValue()?1:0);	// to /unsigned/ byte u from Boolean tt u = (byte)(tt.booleanValue()?1:0);	// to short s from Boolean tt s = (short)(tt.booleanValue()?1:0);	// to char c from Boolean tt // to get '0' and '1' c = (char)(tt.booleanValue()?'1':'0'); // or to get Unicode 0 and 1 c = (char)(tt.booleanValue()?0:1);	// to int i from Boolean tt i = tt.booleanValue()?1:0;	// to long n from Boolean tt n = tt.booleanValue()?1:0;	// to float f from Boolean tt f = tt.booleanValue()?1:0;	// to double d from Boolean tt d = tt.booleanValue()?1:0;	// to String g from Boolean tt g = tt.toString();	--------	// to /signed/ Byte bb from Boolean tt bb = new Byte((byte)(tt.booleanValue()?1:0));	// to /unsigned/ Byte uu from Boolean tt uu = new Byte((byte)(tt.booleanValue()?1:0));	// to Short ss from Boolean tt ss = new Short((short)(tt.booleanValue()?1:0));	// to Character cc from Boolean tt // to get '0' and '1' cc = new Character((char)(tt.booleanValue()?'1':'0')); // or to get Unicode 0 or 1 cc = new Character((char)(tt.booleanValue()?1:0));	// to Integer ii from Boolean tt // best JDK 1.5+ ii = Integer.valueOf(tt.booleanValue()?1:0); // or JDK 1.4- ii = new Integer(tt.booleanValue()?1:0);	// to Long nn from Boolean tt // best JDK 1.5+ nn = Long.valueOf(tt.booleanValue()?1:0); // or JDK 1.4- nn = new Long(tt.booleanValue()?1:0);	// to Float ff from Boolean tt ff = new Float(tt.booleanValue()?1:0);	// to Double dd from Boolean tt dd = new Double(tt.booleanValue()?1:0);	Boolean tt
/signed/ Byte bb	// to boolean t from /signed/ Byte bb t = bb.byteValue() != 0;	// to /signed/ byte b from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to /unsigned/ byte u from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to short s from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to char c from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to int i from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to long n from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to float f from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to double d from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to String g from /signed/ Byte bb g = bb.toString();	// to Boolean tt from /signed/ Byte bb // best tt = (bb.byteValue() != '0') ? Boolean.TRUE : Boolean.FALSE; // or tt = (bb.byteValue() != 0) ? Boolean.TRUE : Boolean.FALSE;	--------	// to /unsigned/ Byte uu from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to Short ss from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to Character cc from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to Integer ii from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to Long nn from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to Float ff from /signed/ Byte bb // no conversion necessary in Java 1.5+	// to Double dd from /signed/ Byte bb // no conversion necessary in Java 1.5+	/signed/ Byte bb
/unsigned/ Byte uu	// to boolean t from /unsigned/ Byte uu t = uu.byteValue() != 0;	// to /signed/ byte b from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to /unsigned/ byte u from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to short s from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to char c from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to int i from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to long n from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to float f from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to double d from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to String g from /unsigned/ Byte uu g = uu.toString();	// to Boolean tt from /unsigned/ Byte uu // best tt = (uu.byteValue() != '0') ? Boolean.TRUE : Boolean.FALSE; // or tt = (uu.byteValue() != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	--------	// to Short ss from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to Character cc from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to Integer ii from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to Long nn from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to Float ff from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	// to Double dd from /unsigned/ Byte uu // no conversion necessary in Java 1.5+	/unsigned/ Byte uu
Short ss	// to boolean t from Short ss t = ss.shortValue() != 0;	// to /signed/ byte b from Short ss b = (byte)ss.shortValue();	// to /unsigned/ byte u from Short ss u = (byte)ss.shortValue();	// to short s from Short ss // no conversion necessary in Java 1.5+	// to char c from Short ss // no conversion necessary in Java 1.5+	// to int i from Short ss // no conversion necessary in Java 1.5+	// to long n from Short ss // no conversion necessary in Java 1.5+	// to float f from Short ss // no conversion necessary in Java 1.5+	// to double d from Short ss // no conversion necessary in Java 1.5+	// to String g from Short ss g = ss.toString();	// to Boolean tt from Short ss // best tt = (ss.shortValue() != '0') ? Boolean.TRUE : Boolean.FALSE; // or tt = (ss.shortValue() != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from Short ss bb = new Byte(ss.byteValue());	// to /unsigned/ Byte uu from Short ss uu = new Byte(ss.byteValue());	--------	// to Character cc from Short ss // no conversion necessary in Java 1.5+	// to Integer ii from Short ss // no conversion necessary in Java 1.5+	// to Long nn from Short ss // no conversion necessary in Java 1.5+	// to Float ff from Short ss // no conversion necessary in Java 1.5+	// to Double dd from Short ss // no conversion necessary in Java 1.5+	Short ss
Character cc	// to boolean t from Character cc // to convert '0' or '1' t = cc.charValue() != '0'; // to convert Unicode 0 or 1 t = cc.charValue() != 0;	// to /signed/ byte b from Character cc // international b = (byte)Character.digit(cc.charValue(), 10 /* radix */); // fastest '9' -> 9 b = (byte)(cc.charValue() - '0'); // or to get Unicode value b = (byte)cc.charValue();	// to /unsigned/ byte u from Character cc // international u = (byte)Character.digit(cc.charValue(), 10 /* radix */); // fastest '9' -> 9 u = (byte)(cc.charValue() - '0'); // or to get Unicode value u = (byte)cc.charValue();	// to short s from Character cc // no conversion necessary in Java 1.5+	// to char c from Character cc // no conversion necessary in Java 1.5+	// to int i from Character cc // no conversion necessary in Java 1.5+	// to long n from Character cc // no conversion necessary in Java 1.5+	// to float f from Character cc // no conversion necessary in Java 1.5+	// to double d from Character cc // no conversion necessary in Java 1.5+	// to String g from Character cc g = cc.toString();	// to Boolean tt from Character cc // for '0' or '1' tt = (cc.charValue() != '0') ? Boolean.TRUE : Boolean.FALSE; // or for Unicode 0 or 1 tt = (cc.charValue() != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from Character cc // international bb = new Byte((byte)Character.digit(cc.charValue(), 10 /* radix */)); // fastest '9' -> 9 bb = new Byte((byte)(cc.charValue() - '0')); // or to get Unicode value bb = new Byte((byte)cc.charValue());	// to /unsigned/ Byte uu from Character cc // international uu = new Byte((byte)Character.digit(cc.charValue(), 10 /* radix */)); // fastest '9' -> 9 uu = new Byte((byte)(cc.charValue() - '0')); // or to get Unicode value uu = new Byte((byte)cc.charValue());	// to Short ss from Character cc // no conversion necessary in Java 1.5+	--------	// to Integer ii from Character cc // no conversion necessary in Java 1.5+	// to Long nn from Character cc // no conversion necessary in Java 1.5+	// to Float ff from Character cc // no conversion necessary in Java 1.5+	// to Double dd from Character cc // no conversion necessary in Java 1.5+	Character cc
Integer ii	// to boolean t from Integer ii t = ii.intValue() != 0;	// to /signed/ byte b from Integer ii b = (byte)ii.intValue();	// to /unsigned/ byte u from Integer ii u = (byte)ii.intValue();	// to short s from Integer ii s = (short)ii.intValue();	// to char c from Integer ii c = (char)ii.intValue();	// to int i from Integer ii // no conversion necessary in Java 1.5+	// to long n from Integer ii // no conversion necessary in Java 1.5+	// to float f from Integer ii // no conversion necessary in Java 1.5+	// to double d from Integer ii // no conversion necessary in Java 1.5+	// to String g from Integer ii g = ii.toString();	// to Boolean tt from Integer ii tt = (ii.intValue() != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from Integer ii bb = new Byte(ii.byteValue());	// to /unsigned/ Byte uu from Integer ii uu = new Byte(ii.byteValue());	// to Short ss from Integer ii ss = new Short(ii.shortValue());	// to Character cc from Integer ii // 9 -> '9' cc = new Character((char)(ii.intValue() + '0')); // or to get Unicode value cc = new Character((char)ii.intValue());	--------	// to Long nn from Integer ii // no conversion necessary in Java 1.5+	// to Float ff from Integer ii // no conversion necessary in Java 1.5+	// to Double dd from Integer ii // no conversion necessary in Java 1.5+	Integer ii
Long nn	// to boolean t from Long nn t = nn.longValue() != 0;	// to /signed/ byte b from Long nn b = (byte)nn.intValue();	// to /unsigned/ byte u from Long nn u = (byte)nn.intValue();	// to short s from Long nn s = (short)nn.intValue();	// to char c from Long nn // 9 -> '9' c = (char)(nn.intValue() + '0'); // or to get Unicode value c = (char)nn.intValue();	// to int i from Long nn i = nn.intValue();	// to long n from Long nn // no conversion necessary in Java 1.5+	// to float f from Long nn // no conversion necessary in Java 1.5+	// to double d from Long nn // no conversion necessary in Java 1.5+	// to String g from Long nn g = nn.toString();	// to Boolean tt from Long nn tt = (nn.longValue() != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from Long nn bb = new Byte(nn.byteValue());	// to /unsigned/ Byte uu from Long nn uu = new Byte(nn.byteValue());	// to Short ss from Long nn ss = new Short(nn.shortValue());	// to Character cc from Long nn // 9 -> '9' cc = new Character((char)(nn.intValue() + '0')); // or to get Unicode value cc = new Character((char)nn.intValue());	// to Integer ii from Long nn // best JDK 1.5+ ii = Integer.valueOf(nn.intValue()); // or JDK 1.4- ii = new Integer(nn.intValue());	--------	// to Float ff from Long nn // no conversion necessary in Java 1.5+	// to Double dd from Long nn // no conversion necessary in Java 1.5+	Long nn
Float ff	// to boolean t from Float ff t = ff.floatValue() != 0;	// to /signed/ byte b from Float ff b = (byte)ff.intValue();	// to /unsigned/ byte u from Float ff u = (byte)ff.intValue();	// to short s from Float ff s = (short)ff.intValue();	// to char c from Float ff c = (char)ff.intValue();	// to int i from Float ff i = ff.intValue();	// to long n from Float ff n = ff.longValue();	// to float f from Float ff // no conversion necessary in Java 1.5+	// to double d from Float ff // no conversion necessary in Java 1.5+	// to String g from Float ff // 2 decimal places, rounded, locale-sensitive java.text.DecimalFormat df2 = new java.text.DecimalFormat("###,##0.00"); g = df2.format(ff.floatValue()); // or exponential scientific format, locale-sensitive. java.text.DecimalFormat de = new java.text.DecimalFormat("0.000000E00"); g = de.format(ff.floatValue()); // or best for readability and maintainability, locale-insensitive. g = ff.toString();	// to Boolean tt from Float ff tt = (ff.floatValue() != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from Float ff bb = new Byte(ff.byteValue());	// to /unsigned/ Byte uu from Float ff uu = new Byte(ff.byteValue());	// to Short ss from Float ff ss = new Short(ff.shortValue());	// to Character cc from Float ff cc = new Character((char)ff.intValue());	// to Integer ii from Float ff // best JDK 1.5+ ii = Integer.valueOf(ff.intValue()); // or JDK 1.4- ii = new Integer(ff.intValue());	// to Long nn from Float ff // best JDK 1.5+ nn = Long.valueOf(ff.longValue()); // or JDK 1.4- nn = new Long(ff.longValue());	--------	// to Double dd from Float ff // no conversion necessary in Java 1.5+	Float ff
Double dd	// to boolean t from Double dd t = dd.doubleValue() != 0;	// to /signed/ byte b from Double dd b = (byte)dd.intValue();	// to /unsigned/ byte u from Double dd u = (byte)dd.intValue();	// to short s from Double dd s = (short)dd.intValue();	// to char c from Double dd c = (char)dd.intValue();	// to int i from Double dd i = dd.intValue();	// to long n from Double dd n = dd.longValue();	// to float f from Double dd f = dd.floatValue();	// to double d from Double dd // no conversion necessary in Java 1.5+	// to String g from Double dd // 2 decimal places, rounded, locale-sensitive java.text.DecimalFormat df2 = new java.text.DecimalFormat("###,##0.00"); g = df2.format(dd.doubleValue()); // or exponential scientific format, locale sensitive. java.text.DecimalFormat de = new java.text.DecimalFormat("0.0000000000E00"); g = de.format(dd.doubleValue()); // or best for readability and maintainability, locale-insensitive g = dd.toString();	// to Boolean tt from Double dd tt = (dd.doubleValue() != 0) ? Boolean.TRUE : Boolean.FALSE;	// to /signed/ Byte bb from Double dd bb = new Byte(dd.byteValue());	// to /unsigned/ Byte uu from Double dd uu = new Byte(dd.byteValue());	// to Short ss from Double dd ss = new Short(dd.shortValue());	// to Character cc from Double dd cc = new Character((char)dd.intValue());	// to Integer ii from Double dd // best JDK 1.5+ ii = Integer.valueOf(dd.intValue()); // or JDK 1.4- ii = new Integer(dd.intValue());	// to Long nn from Double dd // best JDK 1.5+ nn = Long.valueOf(dd.longValue()); // or JDK 1.4- nn = new Long(dd.longValue());	// to Float ff from Double dd ff = new Float(dd.floatValue());	--------	Double dd
	to: boolean t	to: /signed/ byte b	to: /unsigned/ byte u	to: short s	to: char c	to: int i	to: long n	to: float f	to: double d	to: String g	to: Boolean tt	to: /signed/ Byte bb	to: /unsigned/ Byte uu	to: Short ss	to: Character cc	to: Integer ii	to: Long nn	to: Float ff	to: Double dd

Primitives

Primitive variables include boolean, char, byte, short, int, long, float and double. Strings, arrays and Objects are not considered primitives.

Java Primitives
Type	Signed?	Bits	Bytes	Digits	Lowest	Highest	Mnemonic
boolean	n/a	1	1	1	false	true	zero/one
char	unsigned Unicode	16	2	4:5	'\u0000' [0] aka Character.MIN_VALUE	'\uffff' [2¹⁶-1] aka Character.MAX_VALUE	Unicode chars are twice as big as C’s.
byte	signed	8	1	2:3	-128 [-2⁷] aka Byte.MIN_VALUE	+127 [2⁷-1]aka Byte.MAX_VALUE	Bytes are signed, so half the usual 255 range.
short	signed	16	2	4:5	-32,768 [-2¹⁵] aka Short.MIN_VALUE	+32,767 [2¹⁵-1] aka Short.MAX_VALUE	32K
int	signed	32	4	9:10	-2,147,483,648 [-2³¹] aka Integer.MIN_VALUE	+2,147,483,647 [2³¹-1] aka Integer.MAX_VALUE	2 gig
long	signed	64	8	18:19	-9,223,372,036,854,775,808 [-2⁶³] aka Long. MIN_VALUE	+9,223,372,036,854,775,807 [2⁶³-1] aka Long. MAX_VALUE	9 exabytes, or 9 billion gig
float	signed exponent and mantissa	32	4	6:7	±1.40129846432481707e-45 aka Float.MIN_VALUE	±3.40282346638528860e+38 aka Float.MAX_VALUE or roughly ±2¹²⁷ with 6 to 7 significant digits of accuracy. A float can exactly represent integers in the range -2²⁴ to +2²⁴.	rough, compact float
double	signed exponent and mantissa	64	8	14:15	±4.94065645841246544e-324 aka Double.MIN_VALUE	±1.79769313486231570e+308 aka Double.MAX_VALUE or roughly ±2¹⁰²³ with 14 to 15 significant digits of accuracy. A double can exactly represent integers in the range -2⁵³ to +2⁵³.	high precision float

Primitives vs Immutable Wrapper Objects

Contrast that table of primitives, with this table of basic Java types:

Mutable Primitives	Immutable Objects
boolean	Boolean
ordinary signed byte	Byte
unsigned byte	Byte
short	Short
char	Character
int	Integer
long	Long
float	Float
double	Double
char[]	String

Truncation

If a long is converted to an int, or an int to a byte, the high order bits are simply truncated. This can result in surprising results including sign reversal.

byte[] ⇔ String

Interconverting byte [] and String is tricky because there is always an implied encoding translation. "8859_1" encoding simply chops the high byte off or pads the high byte with 0s, what newbies erroneously imagine happens all the time.

String s = "abc";
// string -> byte[]
byte [] b = s.getBytes( "8859_1" /* encoding */ );
// byte[] -> String
String t = new String( b , "Cp1252" /* encoding */ );

char[] ⇔ String

Interconverting char [] and String is easier because there is no encoding involved. Encoding is about how to represent 16-bit Unicode in 8-bit bytes.

String s = "abc" ;
// string -> char[]
char[] ca = s.toCharArray();
// char[] -> String
String s = new String( ca );

Beware of char[].toString(). It does not convert the character array to String. It prints out the address of the array — not useful for anything. Use new String ( chararray ) instead.

Hexadecimal

The radix feature of the toString and parseInt methods lets you handle hexadecimal numbers. Just set the radix to 16.

StringBuffers & StringBuilders

Strings and StringBuffers can be interconverted, as can Strings and StringBuilders

Rounding

Rounding often surprises because fractions like 0.1 cannot be precisely be represented in IEEE floating point format. Often you find yourself having to add tiny numbers just prior to printing to get the desired effects.

// Rounding to an integer:
long n = Math.round(d);
double d = Math.rint(d);

// Rounding to two decimal places:
long n = Math.round(d *100.); /* keep as "pennies" */
double d = Math.rint (d *100.)/100.;

floating point for more details.

Left Zeros

The standard conversions give you no leading blanks or leading zeroes. Here is a code snippet to convert an int to a String padded with leading left zeroes. With an obvious modification it would give you lead blanks.

Formatted Output

JDK 1.0.2 has no function like C’s printf that lets you control how many positions and decimal places you want in your output. You have to roll your own.

JDK 1.1+ has formatting picture classes such as java.util.DateFormat, SimpleDateFormat and DecimalFormat.

Formatting is such a common request, you might attain sainthood if you wrote a formatting class that gives you all the power of printf without the overhead of parsing strings for % produce a string. e.g.

Java 1.5+, java.io. PrintWriter. printf, java.io. PrintStream. printf and the java.util. Formatter class give you abilities similar to C’s printf. See printf for more details.

Reading Numeric Data From an ASCII file

Java has no built-in methods for reading data of the form: 123 456,-4.

You have to roll your own method. You may be able to use my CSVReader class. Or use java.io.StreamTokenizer or java.util.StringTokenizer, perhaps in combination with readLine to get your data into strings. StreamTokenizer has bells and whistles to deal with parsing source code, including white space, comments and numbers. StringTokenizer just splits the text up based on delimiter characters. Then use the conversion methods in the table above to convert to integers etc. See below for a simplified examples of how you would do this.

StreamTokenizer Method Of Reading Integers From An ASCII File

StringTokenizer Method Of Reading Integers From An ASCII file

Binary

Binary is a compact, machine-friendly, human-unintelligible format. For human readable i/o, Java works with Strings of characters. You separately convert these to and from internal binary format e.g. int. See the conversion Amanuensis for how.

conversion
conversion table for Java 1.4-
Converter Amanuensis
DecimalFormat

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