synchronized细节问题

锁重入：

/*** synchronized的重入*/
public class SyncDubbo1 {public synchronized void method1(){System.out.println("method1..");method2();}public synchronized void method2(){System.out.println("method2..");method3();}public synchronized void method3(){System.out.println("method3..");}public static void main(String[] args) {final SyncDubbo1 sd = new SyncDubbo1();Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {sd.method1();}});t1.start();}
}

/*** synchronized异常*/
public class SyncException {private int i = 0;public synchronized void operation(){while(true){try {i++;Thread.sleep(100);System.out.println(Thread.currentThread().getName() + " , i = " + i);if(i == 10){Integer.parseInt("a");//throw new RuntimeException();}} catch (Exception e) {e.printStackTrace();System.out.println(" log info i = " + i);}}}public static void main(String[] args) {final SyncException se = new SyncException();Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {se.operation();}},"t1");t1.start();}}

/*** synchronized异常*/
public class SyncException {private int i = 0;public synchronized void operation(){while(true){try {i++;Thread.sleep(100);System.out.println(Thread.currentThread().getName() + " , i = " + i);if(i == 10){Integer.parseInt("a");//throw new RuntimeException();}} catch (InterruptedException e) {e.printStackTrace();System.out.println(" log info i = " + i);throw new RuntimeException();//continue;}}}public static void main(String[] args) {final SyncException se = new SyncException();Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {se.operation();}},"t1");t1.start();}}

/*** 使用synchronized代码块加锁,比较灵活*/
public class ObjectLock {public void method1(){synchronized (this) {    //对象锁try {System.out.println("do method1..");Thread.sleep(2000);} catch (InterruptedException e) {e.printStackTrace();}}}public void method2(){       //类锁synchronized (ObjectLock.class) {try {System.out.println("do method2..");Thread.sleep(2000);} catch (InterruptedException e) {e.printStackTrace();}}}private Object lock = new Object();public void method3(){       //任何对象锁synchronized (lock) {try {System.out.println("do method3..");Thread.sleep(2000);} catch (InterruptedException e) {e.printStackTrace();}}}public static void main(String[] args) {final ObjectLock objLock = new ObjectLock();Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {objLock.method1();}});Thread t2 = new Thread(new Runnable() {@Overridepublic void run() {objLock.method2();}});Thread t3 = new Thread(new Runnable() {@Overridepublic void run() {objLock.method3();}});t1.start();t2.start();t3.start();}}

/*** synchronized代码块对字符串的锁，注意String常量池的缓存功能*/
public class StringLock {public void method() {//new String("字符串常量")synchronized (new String("字符串常量")) {try {while(true){System.out.println("当前线程 : "  + Thread.currentThread().getName() + "开始");Thread.sleep(1000);     System.out.println("当前线程 : "  + Thread.currentThread().getName() + "结束");}} catch (InterruptedException e) {e.printStackTrace();}}}public static void main(String[] args) {final StringLock stringLock = new StringLock();Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {stringLock.method();}},"t1");Thread t2 = new Thread(new Runnable() {@Overridepublic void run() {stringLock.method();}},"t2");t1.start();t2.start();}
}

/*** 锁对象的改变问题*/
public class ChangeLock {private String lock = "lock";private void method(){synchronized (lock) {try {System.out.println("当前线程 : "  + Thread.currentThread().getName() + "开始");lock = "change lock";Thread.sleep(2000);System.out.println("当前线程 : "  + Thread.currentThread().getName() + "结束");} catch (InterruptedException e) {e.printStackTrace();}}}public static void main(String[] args) {final ChangeLock changeLock = new ChangeLock();Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {changeLock.method();}},"t1");Thread t2 = new Thread(new Runnable() {@Overridepublic void run() {changeLock.method();}},"t2");t1.start();try {Thread.sleep(100);} catch (InterruptedException e) {e.printStackTrace();}t2.start();}}

/*** 同一对象属性的修改不会影响锁的情况*/
public class ModifyLock {private String name ;private int age ;public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public synchronized void changeAttributte(String name, int age) {try {System.out.println("当前线程 : "  + Thread.currentThread().getName() + " 开始");this.setName(name);this.setAge(age);System.out.println("当前线程 : "  + Thread.currentThread().getName() + " 修改对象内容为： " + this.getName() + ", " + this.getAge());Thread.sleep(2000);System.out.println("当前线程 : "  + Thread.currentThread().getName() + " 结束");} catch (InterruptedException e) {e.printStackTrace();}}public static void main(String[] args) {final ModifyLock modifyLock = new ModifyLock();Thread t1 = new Thread(new Runnable() {@Overridepublic void run() {modifyLock.changeAttributte("张三", 20);}},"t1");Thread t2 = new Thread(new Runnable() {@Overridepublic void run() {modifyLock.changeAttributte("李四", 21);}},"t2");t1.start();try {Thread.sleep(100);} catch (InterruptedException e) {e.printStackTrace();}t2.start();}}

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