你真得会写java多线程手撕代码题吗？Javazycxnanwang的博客-

你真得会写java多线程手撕代码题吗？

多线程部分是java中最重要的一部分之一，所以也是面试官经常问的部分。

头条面试的时候，经常会让你手撕一些多线程代码题。下面介绍几个经典

得面试题

两个线程，线程1打印A，线程2打印B,两个线程同时并发，要求保证先打印A,后打印B

使用synchronized+ wait、notify

public class Main{ static class Number{ public int num = 1; Number(){} } public static  Number number = new Number(); public static void main(String []args) {         Thread a = new Thread(new Runnable(){ @Override public void run() { synchronized(number){ try{ //避免假唤醒 while(number.num == 2) number.wait(); }catch(Exception e) {                         e.printStackTrace(); }                     System.out.println("A");                     number.num = 2;                     number.notify(); } } });          Thread b = new Thread(new Runnable(){ @Override public void run() { synchronized(number) { try{ while(number.num == 1) number.wait(); }catch(Exception e){                         e.printStackTrace(); }                     System.out.println("B");                     number.num = 1;                     number.notify(); } } });         b.start(); try{             Thread.sleep(1000); }catch(Exception e) {             e.printStackTrace(); }         a.start(); } } 

使用ReetrantLock+Condition

import java.util.concurrent.locks.*; public class Main{ public static  ReentrantLock lock = new ReentrantLock(); public static Condition condition = lock.newCondition(); public static int num = 1; public static void main(String []args) {         Thread a = new Thread(new Runnable(){ @Override public void run() {                 lock.lock(); try{ while(num == 2) condition.await(); }catch(Exception e) {                     e.printStackTrace(); }                 System.out.println("A");                 num = 2;                 condition.signal();                 lock.unlock(); } });          Thread b = new Thread(new Runnable(){ @Override public void run() {                 lock.lock(); try{ while(num == 1) condition.await(); }catch(Exception e) {                     e.printStackTrace(); }                 System.out.println("B");                 num = 1;                 condition.signal();                 lock.unlock(); } });         b.start(); try{             Thread.sleep(1000); }catch(Exception e){             e.printStackTrace(); };         a.start(); } } 

两个线程，一个线程打印奇数，一个线程打印偶数，控制先一个奇数后一个偶数这种顺序.使用ReetrantLock+Condition

import java.util.concurrent.locks.*; public class Main{ public static  ReentrantLock lock = new ReentrantLock(); public static Condition condition = lock.newCondition(); public static int num = 2; public static void main(String []args) {         Thread a = new Thread(new Runnable(){ @Override public void run() { try{ for(int i = 2; i <= 10; i=i+2) {                         lock.lock(); while(num == 2) condition.await();                         System.out.print(i);                         num = 2; condition.signal();                         lock.unlock(); } }catch(Exception e) {                     e.printStackTrace(); } } });          Thread b = new Thread(new Runnable(){ @Override public void run() { try{ for(int i = 1; i <= 10; i = i+2){                         lock.lock(); while(num == 1) condition.await();                         System.out.print(i);                         num = 1; condition.signal();                         lock.unlock(); } }catch(Exception e) {                     e.printStackTrace(); } } });         a.start(); try{             Thread.sleep(10); }catch(Exception e){             e.printStackTrace(); };         b.start(); } } 

参考文献

JAVA线程间通信的几种方式