stackofints.java

java tutorial.sun公司官方出品。java入门书籍。最新版

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 *     from this software without specific prior written permission.
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 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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 */ 

public class StackOfInts {
	
	private int[] stack;
	private int next = 0;  // index of last item in stack + 1
	
	public StackOfInts(int size) {
		//create an array large enough to hold the stack
		stack = new int[size];
	}
	
	public void push(int on) {
		if (next < stack.length)
		   stack[next++] = on;
	}
	public boolean isEmpty() {
		return (next == 0);
	}
	
	public int pop(){
		if (!isEmpty()) 
		   return stack[--next]; // top item on stack
		else
		   return 0;
	}
	
	public int getStackSize() {
		return next;
	}
	
	private class StepThrough { 		
		// start stepping through at i=0
		private int i = 0; 
		
		// increment index
		public void increment() {
			if ( i < stack.length)
			   i++;
		}
		
		// retrieve current element
		public int current() {
			return stack[i];
		}
		
		// last element on stack?
		public boolean isLast(){
			if (i == getStackSize() - 1)
			   return true;
			else
			   return false;
		}
	}
	
	public StepThrough stepThrough() {
		return new StepThrough();
	}
	
	public static void main(String[] args) {
		
		// instantiate outer class as "stackOne"
		StackOfInts stackOne = new StackOfInts(15);
		
		// populate stackOne
		for (int j = 0 ; j < 15 ; j++) {
			stackOne.push(2*j);
		}
		
		// instantiate inner class as "iterator"
		StepThrough iterator = stackOne.stepThrough();
		
		// print out stackOne[i], one per line
		while(!iterator.isLast()) {
			System.out.print(iterator.current() + " ");
			iterator.increment();
		}
		System.out.println();
		
	}
	
}