java 实现栈，java实现

java 实现栈，java实现

Java 已为我们实现了栈，先用Java 自己自带的Stack类。

package sort;

import java.util.Stack;

public class StackDemo_1 {
    public static void main(String[] args) {
        Stack<String> stack = new Stack<String>();
        for (int i=0; i<10; i++) {
            stack.push("" + i);
        }
        
        System.out.println(stack.size());
        
        int length = stack.size();
        for (int i=0; i<length; i++) {
            System.out.println(stack.size() + ":  " + stack.pop());
        } 
    }
}

现在自己用数组来实现：

package sort;

/**
 * @author Brook Lieu
 * @version v1.0 2014-9-29
 */
public class StackDemo_1 {
    /**
     * 测试
     * @param args
     */
    public static void main(String[] args) {
        Stack_1<String> stack_1 = new Stack_1<String>();
        
        for (int i=0; i<10; i++) {
            stack_1.push("" + i);
        }
        
        int stackSize = stack_1.getStackSize();
        System.out.println("stack Size is " + stackSize);
        for (int i=0; i<stackSize; i++) {
            System.out.println(i + ": " + stack_1.pop());
        }
        
        stack_1.pop();
    }
}

package sort;

import java.util.Arrays;

public class Stack_1<T> {
    T[] objectDatas;
    int top = -1;
    int capsualSize = 10;
    int size;
    
    @SuppressWarnings("unchecked")
    public Stack_1() {
        objectDatas = (T[]) new Object[capsualSize];
    }
    
    // 插入
    public void push(T t) {
       mesureSize();
       objectDatas[++top] = t;
    }
    
    public T pop() {
        if (!isEmpty()) {
            return objectDatas[top--];
        } else {
            throw new RuntimeException("栈已为空，不能再取值");
        }
    }
    
    public boolean isEmpty() {
        return top == -1;
    }
    
    public int getStackSize() {
        return top + 1;
    }
    
    /**
     * 确保栈空间够用
     */
    private void mesureSize() {
        if (top >= capsualSize-1) {
            capsualSize = 2 * capsualSize;
            @SuppressWarnings("unchecked")
            T[] tempT = (T[]) new Object[capsualSize];
            tempT = Arrays.copyOfRange(objectDatas, 0, top);
            
            objectDatas = tempT;
        }
    }
}

输出结果为：

Exception in thread "main" stack Size is 10
0: 9
1: 8
2: 7
3: 6
4: 5
5: 4
6: 3
7: 2
8: 1
9: 0
java.lang.RuntimeException: 栈已为空，不能再取值
	at sort.Stack_1.pop(Stack_1.java:26)
	at sort.StackDemo_1.main(StackDemo_1.java:20)