手撕代码简单例子

死锁

public class DeadLockDemo {
    public void method1() {
        synchronized (String.class) {
            System.out.println("method1 lock1……");
            synchronized (Integer.class) {
                System.out.println("method1 lock2……");
            }
        }
    }

    public void method2() {
        synchronized (Integer.class) {
            System.out.println("method2 lock1……");
            synchronized (String.class) {
                System.out.println("method2 lock2……");
            }
        }
    }
}

单例模式

饿汉式
class Singleton {
 private static Singleton instance=new Singleton();
 private Singleton(){}
 static Singleton getInstance() {
 return instance;
 }
}

懒汉式
class Singleton {
 private static Singleton instance=null;
 private Singleton(){}
 static Singleton getInstance() {
 if(instance==null)
 instance=new Singleton();
 return instance;
 }
}