synchronized关键字的用法
1、class monitor
public synchronized static void staticSync()
synchronized (ClassMonitor.class)
2、this monitor
public synchronized void sync()
synchronized (this)
3、monitor
private final Object object= new Object();
synchronized (object)
使用举例
1、类锁
// 类锁 class
public void method_class() {
try {
System.out.println(Thread.currentThread().getName() + " 方法开始");
synchronized (Service.class) {
extracted();
}
System.out.println(Thread.currentThread().getName() + " 方法结束");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
// 类锁 static syn
public static synchronized void method_syn_static() {
try {
System.out.println(Thread.currentThread().getName() + " 方法开始");
extracted();
System.out.println(Thread.currentThread().getName() + " 方法结束");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
2、对象锁
// 对象锁 synchronized
public synchronized void method_syn() {
try {
System.out.println(Thread.currentThread().getName() + " 方法开始");
extracted();
System.out.println(Thread.currentThread().getName() + " 方法结束");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
// 对象锁 this
public void method_this() {
try {
System.out.println(Thread.currentThread().getName() + " 方法开始");
synchronized (this) {
extracted();
}
System.out.println(Thread.currentThread().getName() + " 方法结束");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
3、私有锁
private String lock = new String();
// 私有锁
public void method_pri_lock() {
try {
System.out.println(Thread.currentThread().getName() + " 方法开始");
synchronized (lock) {
extracted();
}
System.out.println(Thread.currentThread().getName() + " 方法结束");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
// 局部私有锁
public void method_loc_lock() {
try {
System.out.println(Thread.currentThread().getName() + " 方法开始");
String lock = new String();
synchronized (lock) {
extracted();
}
System.out.println(Thread.currentThread().getName() + " 方法结束");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
总结:
1、每个类只有一个类锁
2、每个对象对应一个对象锁
3、类锁
,对象锁
,私有锁
彼此之间不会产生竞争
类锁,对象锁,私有锁,竞争分析