java 使用两个栈实现队列

public class StackToQueue {
private static final String TAG  ="StackToQueue";
public Stack<TestBean> fStack = new Stack<>();
public Stack<TestBean> sStack = new Stack<>();

public void insert(TestBean bean){
fStack.push(bean);
}

public TestBean delete(){
//just print data
for (int z = 0; z < fStack.size(); z++) {
//System.out.println(TAG+"--print current fStack--"+fStack.get(z).name);
}
//clear sStack
for (int i = 0; i < sStack.size(); i++) {
sStack.pop();
}
//put data to sStack
int sizeOrigin = fStack.size();
for (int i = 0; i < sizeOrigin; i++) {
sStack.push(fStack.pop());
}
//just print data
for (int z = 0; z < sStack.size(); z++) {
//System.out.println(TAG+"--to sStack--"+sStack.get(z).name);
}

TestBean t = sStack.pop();
int currentSize = sStack.size();
for (int i = 0; i < currentSize; i++) {
fStack.push(sStack.pop());
}
//just print data
for (int z = 0; z < fStack.size(); z++) {
//System.out.println(TAG+"--to fStack--"+fStack.get(z).name);
}
return t;
}

public static class TestBean{
public TestBean(String name) {
this.name = name;
}

String name;
}

public static void test(){
StackToQueue s = new StackToQueue();
for (int i = 0; i < 4; i++) {
s.insert(new TestBean(TAG+"index="+i));
}
System.out.println(TAG+"======check sStack====");
for (int i = 0; i < 4; i++) {
System.out.println(TAG+"=="+s.fStack.get(i).name);
}
for (int i = 0; i < 4; i++) {
System.out.println(TAG+"======delete====");
System.out.println(TAG+"=s.delete().name="+s.delete().name);
for (int z = 0; z < s.fStack.size(); z++) {
System.out.println(TAG+"=="+s.fStack.get(z).name);
}
}

}
}

=====result=====

12-05 14:41:20.870 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue======check sStack====
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue==StackToQueueindex=0
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue==StackToQueueindex=1
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue==StackToQueueindex=2
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue==StackToQueueindex=3
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue======delete====
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue=s.delete().name=StackToQueueindex=0
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue==StackToQueueindex=1
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue==StackToQueueindex=2
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue==StackToQueueindex=3
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue======delete====
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue=s.delete().name=StackToQueueindex=1
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue==StackToQueueindex=2
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue==StackToQueueindex=3
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue======delete====
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue=s.delete().name=StackToQueueindex=2
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue==StackToQueueindex=3
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue======delete====
12-05 14:41:20.871 2727-2727/com.example.bxh.sayhello I/System.out: StackToQueue=s.delete().name=StackToQueueindex=3

==============
可以想象一下，有两个“直径比乒乓球略大”的杯子A&B，向A中放进去四个乒乓球，最底下的是0号球，最上面的是3号球，这时候希望取出最底下的乒乓球，即0号球，此时将A中的球“一个一个”地放到B中，放完后，B中最上面的球就是0号球，将其取出来以后，再把B中的球一个一个的放进A中，此时A中最底下的球是1号球，最上面的是3号球。至此，达成取出0号球的目的。so，插入&删除 就是此过程的往复。