Java generic stack implementation

by

Examples

package com.w3schools;
 
public class Test<T extends Object> {
    private int stackSize;
    private T[] stackArray;
    private int top;
 
    /**
     * constructor to create stack with size
     * @param size
     */
    public Test(int size) {
        this.stackSize = size;
        this.stackArray = (T[]) new Object[stackSize];
        this.top = -1;
    }
 
    /**
     * Adds new entry to the top of the stack
     * @param entry
     * @throws Exception 
     */
    public void push(T entry) throws Exception {
        if(this.isStackFull()){
        	System.out.println("Stack Overflow");
            this.increaseStackCapacity();
        }
        System.out.println("Adding: "+entry);
        this.stackArray[++top] = entry;
    }
 
    /**
     * Removes an entry from the top of the stack.
     * @return
     * @throws Exception 
     */
    public T pop() throws Exception {
        if(this.isStackEmpty()){
        	System.out.println("Stack underflow.");
        }
        T entry = this.stackArray[top--];
        System.out.println("Removed entry: "+entry);
        return entry;
    }
 
    /**
     * Returns top of the stack without removing it.
     * @return
     */
    public T peek() {
        return stackArray[top];
    }
 
    /**
     * Returns true if the stack is empty
     * @return
     */
    public boolean isStackEmpty() {
        return (top == -1);
    }
 
    /**
     * Returns true if the stack is full
     * @return
     */
    public boolean isStackFull() {
        return (top == stackSize - 1);
    }
 
    /**
     * Increase stack capacity
     */
    private void increaseStackCapacity(){	         
    	T[] newStack = (T[]) new Object[this.stackSize*2];
        for(int i=0;i<stackSize;i++){
            newStack[i] = this.stackArray[i];
        }
        this.stackArray = newStack;
        this.stackSize = this.stackSize*2;
    }
 
	public static void main(String args[]){
		try {
			Test<String> stringStack = new Test<String>(2);
			stringStack.push("w3schools");
			Test<Integer> integerStack = new Test<Integer>(2);
			integerStack.push(13);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Output

Adding: w3schools
Adding: 13