// Computing a histogram, just the basics, no error checking.

// lowest height possible in tenths of an inch
static final int LOWEST = 5 * 12 * 10;

// how wide a range each bin covers in tenths of an inch
static final int BIN_WIDTH = 1 * 10;

// how many bins we will collect
static final int BIN_CAPACITY = 18;

...
// allocate and zero array to store the counts for each bin
int[] bin = new bin[ BIN_CAPACITY ];
for (student : students)
   {
   // height is a given student's height in tenths of a inch
   int height = student.getHeightInDeciInches();

   // figure out which slot this student fits in.
   binNumber = (height - LOWEST) / BIN_WIDTH;

   // increment the appropriate bin for that student's height
   bin[binNumber]++;
   }

// Now feed your bin totals into a bar charting package such as Excel,
// or print them out crudely using *s to represent the bars.