用一个栈给另外一个栈排序

import java.util.Stack;

public class Problem_05_StackSortStack {

public static void sortStackByStack(Stack<Integer> stack) {
    Stack<Integer> help = new Stack<Integer>();
    while (!stack.isEmpty()) {
        int cur = stack.pop();

//核心代码
while (!help.isEmpty() && help.peek() < cur) {
stack.push(help.pop());
}
help.push(cur);
}
while (!help.isEmpty()) {
stack.push(help.pop());
}
}

public static void main(String[] args) {
    Stack<Integer> stack = new Stack<Integer>();
    stack.push(3);
    stack.push(1);
    stack.push(6);
    stack.push(2);
    stack.push(5);
    stack.push(4);
    sortStackByStack(stack);
    System.out.println(stack.pop());
    System.out.println(stack.pop());
    System.out.println(stack.pop());
    System.out.println(stack.pop());
    System.out.println(stack.pop());
    System.out.println(stack.pop());
}

}