Structuring Data with Java - Java - page 279

Example 7-5. ToyStack
public public class class ToyStack ToyStack {

/** The maximum stack depth */
protected protected int int MAX_DEPTH = 10 ;

/** The current stack depth */
protected

protected int int depth = 0 ;

/* The actual stack */
protected protected int int [] stack = new new int int [ MAX_DEPTH ];

/** push - add an element onto the stack */
protected protected void int n ) {

stack [ depth ++] = n ;

void push ( int

}
/** pop - return and remove the top element */
protected

protected int int pop () {

return return stack [-- depth ];

}
/** peek - return the top element but don't remove it */
protected

protected int int peek () {

return return stack [ depth - 1 ];

}

}

If you are not familiar with the basic idea of a stack, you should work through the code here;
if you are familiar with it, you can skip ahead. While looking at it, of course, think about
what happens if pop() or peek() is called when push() has never been called, or if push()
is called to stack more data than will fit.

A second version of this code, ToyStack2 , has been changed to implement my SimpleStack
interface and parameterized, so that we can use it with objects of any type. There is a tiny
performance hit here; the previous version dealt with primitive ints rather than objects.
However, the generality gain is probably more significant: we can use any kind of values in
this stack:

Example 7-6. ToyStack2
/** Toy Stack, converted to SimpleStack interface.
*/
public public class class ToyStack2 ToyStack2 implements implements SimpleStack < Integer > {

/** The maximum stack depth */
protected protected int int MAX_DEPTH = 10 ;

/** The current stack depth */