关于JAVA数据结构中的栈操作

 

package com.stack;


//自定义异常类
public class StackEmptyException extends Exception {

    private static final long serialVersionUID = 1L;
    public StackEmptyException(){
        
    }
    public StackEmptyException(String message){
        super(message);
    }

}

package com.stack;

public interface Stack {
    //返回桟的大小
    public int size();
    //判断桟是否为空
    public boolean isEmpty();
    //数据元素入桟
    public void push(Object o);
    //栈顶元素出栈
    public Object pop() throws StackEmptyException;
    //取出栈顶元素
    public Object peek() throws StackEmptyException;
    //打印输出
    public String print();
}

package com.stack;



public class StackArray implements Stack{

    private final int LEN = 8;
    private Object [] elements;
    private int top;
    
    public StackArray(){
        top = -1;
        elements = new Object[LEN];
    }
    
    @Override
    public int size() {
        return (top +1);
    }

    @Override
    public boolean isEmpty() {
        return top<0;
    }

    @Override
    public void push(Object o) {
        expendSpace();        
        elements[++top] = o;        
    }

    public void expendSpace(){
        if(size()>=LEN){
            Object [] a = new Object[elements.length * 2];
            for(int i=0;i<elements.length;i++){
                a[i] = elements[i];
            }
            elements = a;
        }
    }
    @Override
    public Object pop() throws StackEmptyException {
        if(size()<1){
            throw new StackEmptyException("ERROR!堆栈为空！");
        }
        Object obj = elements[top];
        elements[top--]=null;
        return obj;
    }

    @Override
    public Object peek() throws StackEmptyException {
        if(size()<1){
            throw new StackEmptyException("ERROR！桟为空！");
        }
        return elements[top];
    }

    @Override
    public String print() {
        String str = "(";
        for(int i= 0;i<top+1;i++){
            str += elements[i];
            str +=",";
        }
        str +=")";
        return str;
        
    }
}

package com.stack;

public class Test {

    /**
     * @param args
     * @throws StackEmptyException 
     */
    public static void main(String[] args) throws StackEmptyException {
        StackArray sa = new StackArray();
                //You Code here!!        
    }

}