线程同步synchronized

死锁，同步

TestSync.java

package Thread;public class TestSync implements Runnable{Timer timer = new Timer();public static void main(String[] args) {TestSync test = new TestSync();Thread t1 = new Thread(test);Thread t2 = new Thread(test);t1.setName("t1");t2.setName("t2");t1.start();t2.start();}public void run() {timer.add(Thread.currentThread().getName());}}class Timer{private static int num = 0;public void add(String name){synchronized(this){ //此处使用同步 互斥锁，否则调用t2相同 num++;try {Thread.sleep(1); } catch (Exception e) {}System.out.println(name+ "这是第"+num+"个Timer的add方法");}}}

理解死锁 TestDeadLock.java

package Thread;//模拟死锁,1个线程类模拟2个线程public class TestDeadLock implements Runnable {public int flag = 1;static Object o1 = new Object(), o2 = new Object();public void run() {System.out.println("flag =" + flag);synchronized (o1) {try {Thread.sleep(500);} catch (Exception e) {}synchronized (o2) {try {Thread.sleep(500);} catch (Exception e) {System.out.println("1");}}}if (flag == 0) {synchronized (o2) {try {Thread.sleep(500);} catch (Exception e) {}synchronized (o1) {try {Thread.sleep(500);} catch (Exception e) {System.out.println("0");}}}}}public static void main(String[] args) {TestDeadLock td1 = new TestDeadLock();TestDeadLock td2 = new TestDeadLock();td1.flag = 1;td2.flag = 2;Thread t1 = new Thread(td1);Thread t2 = new Thread(td2);t1.start();t2.start();}}

 

一道面试题,理解直行顺序，程序死锁后，仍然可以直行其他方法

package Thread;public class TT implements Runnable {int b = 100 ;public synchronized void m1() throws Exception{b = 1000;Thread.sleep(5000);System.out.println("b = "+b);}public void m2(){System.out.println(b);}public void run() {try {m1();} catch (Exception e) {e.printStackTrace();}}public static void main(String[] args) throws Exception{TT tt = new TT();Thread t = new Thread(tt);t.start();Thread.sleep(1000);tt.m2();Thread.sleep(6000);}}