多线程面试题_1.三个线程依次打印ABC...2.两个线程交替打印AB，3.生产者消费者
Q：（手写算法）用三个线程，线程“1”，“2”， “3”，顺序打印字母A-Z，输出结果是1A、2B、3C、1D 2E… ？
- 方法1
package com.nancy.base;
public class PrintABC {
private static char c = 'A';
private static int i = 0;
public static void main(String[] args) {
Runnable runnable = new Runnable() {
@Override
public void run() {
synchronized (this) {
try{
int threadId =
Integer.parseInt(Thread.currentThread().getName());
while (i < 26) {
if(i % 3 == threadId - 1) {
System.out.println(threadId + " " + (char) c++);
i++;
notifyAll();
}else {
wait();
}
}
}catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
Thread t1 = new Thread(runnable, "1");
Thread t2 = new Thread(runnable, "2");
Thread t3 = new Thread(runnable, "3");
t1.start();
t2.start();
t3.start();
}
}
1A,2B,3C,1D,2E,3F,1G,2H,3I,1J,2K,3L,1M,2N,3O,1P,2Q,3R,1S,2T,3U,1V,2W,3X,1Y,2Z,
- 方法2
package com.nancy.base;
public class PrintABC2 {
public static int i = 26;
public static Foo foo = new Foo();
public static void main(String[] args) {
new Thread(() -> {
while (i-- > 0) {
foo.print1();
}
}, "1").start();
new Thread(() -> {
while (i-- > 0) {
foo.print2();
}
}, "2").start();
new Thread(() -> {
while (i-- > 0) {
foo.print3();
}
}, "3").start();
}
}
class Foo {
private int flag = 0;
private char c = 'A';
public void print1() {
synchronized (this) {
try {
while (this.flag != 0) {
wait();
}
}catch (InterruptedException e) {
e.printStackTrace();
}
System.out.print(Thread.currentThread().getName() + "" +
(char)c++ + ",");
flag = 1;
notifyAll();
}
}
public void print2() {
synchronized (this) {
try {
while (this.flag != 1) {
wait();
}
}catch (InterruptedException e) {
e.printStackTrace();
}
System.out.print(Thread.currentThread().getName() + "" +
(char)c++ + ",");
flag = 2;
notifyAll();
}
}
public void print3() {
synchronized (this) {
try {
while (this.flag != 2) {
wait();
}
}catch (InterruptedException e) {
e.printStackTrace();
}
System.out.print(Thread.currentThread().getName() + "" +
(char)c++ + ",");
flag = 0;
notifyAll();
}
}
}
1A,2B,3C,1D,2E,3F,1G,2H,3I,1J,2K,3L,1M,2N,3O,1P,2Q,3R,1S,2T,3U,1V,2W,3X,1Y,2Z,
两个线程交替打印AB,总共10次
- 方法1
package com.nancy.base;
public class PrintAB {
private static int flag = 1;
private static int i = 0;
public static void main(String[] args) {
Runnable runnable = new Runnable() {
@Override
public void run() {
synchronized (this) {
try {
int threadId = Integer.parseInt(
Thread.currentThread().getName()
);
while (i < 10) {
if(i % 2 == threadId - 1) {
System.out.print(threadId + "" + (flag == 1 ? 'A' : 'B') + ",");
i++;
flag = -flag;
notifyAll();
}else {
wait();
}
}
}catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
Thread t1 = new Thread(runnable, "1");
Thread t2 = new Thread(runnable, "2");
t1.start();
t2.start();
}
}
1A,2B,1A,2B,1A,2B,1A,2B,1A,2B,
- 方法2
public class PrintAB2 {
public static int DEFUALT_TIMES = 5;
public static void main(String[] args) {
GuardObject lock = new GuardObject();
new Thread(() -> {
int i = DEFUALT_TIMES;
while (i-- > 0) {
lock.printA();
}
}, "1").start();
new Thread(() -> {
int i = DEFUALT_TIMES;
while (i-- > 0) {
lock.printB();
}
}, "2").start();
}
}
class GuardObject {
private boolean flag = true;
public void printA() {
synchronized (this) {
while (!this.flag) {
try {
this.wait();
}catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.print(Thread.currentThread().getName() + "A" + ",");
flag = false;
notifyAll();
}
}
public void printB() {
synchronized (this) {
while (this.flag) {
try {
this.wait();
}catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.print(Thread.currentThread().getName() + "B" + ",");
flag = true;
notifyAll();
}
}
}
1A,2B,1A,2B,1A,2B,1A,2B,1A,2B,
生产者消费者
public class ProductConsumerTest {
public static void main(String[] args) {
Resources r = new Resources();
ProductThread t1 = new ProductThread(r);
ConsumerThread t2 = new ConsumerThread(r);
t1.start();
t2.start();
}
}
class Resources {
private int[] arr = new int[5];
private int count = 0;
synchronized public void product() throws Exception{
if(count == arr.length) {
wait();
}else {
int m = (int)Math.floor(Math.random()*10 + 1);
arr[count] = m;
count++;
System.out.println("生产:" + m);
notifyAll();
}
}
synchronized public void consume() throws Exception {
if(count == 0) {
wait();
}else {
int n = arr[count-1];
arr[count-1] = 0;
count--;
System.out.println("消费：" + n);
notifyAll();
}
}
}
class ProductThread extends Thread {
private Resources r;
public ProductThread(Resources r) {
this.r = r;
}
public void run() {
try {
while (true) {
r.product();
Thread.sleep(1);
}
}catch (Exception e) {
e.printStackTrace();
}
}
}
class ConsumerThread extends Thread {
private Resources r;
public ConsumerThread(Resources r) {
this.r = r;
}
public void run() {
try {
while (true) {
r.consume();
Thread.sleep(1);
}
}catch (Exception e) {
e.printStackTrace();
}
}
}
- 简洁版
public class ProductConsumerTest {
public static void main(String[] args) {
Resources r = new Resources();
new Thread(() -> {
try {
while (true) {
r.product();
Thread.sleep(1);
}
}catch (InterruptedException e) {
e.printStackTrace();
}
}, "生产者").start();
new Thread(() -> {
try {
while (true) {
r.consume();
Thread.sleep(1);
}
}catch (InterruptedException e) {
e.printStackTrace();
}
}, "消费者").start();
}
}
class Resources {
private int[] arr = new int[5];
private int count = 0;
synchronized public void product(){
try {
while (count == arr.length) {
wait();
}
}catch (InterruptedException e) {
e.printStackTrace();
}
int m = (int)Math.floor(Math.random()*10 + 1);
arr[count] = m;
count++;
System.out.println("生产：" + m);
notifyAll();
}
synchronized public void consume() {
try {
while (count == 0) {
wait();
}
}catch (InterruptedException e) {
e.printStackTrace();
}
int m = arr[count-1];
count--;
System.out.println("消费：" + m);
notifyAll();
}
}