Java中的抽象和接口以及单线程

package com.accpeth.demo;public class TestSingleton {public static void main(String[] a){Singleton s1=Singleton.getInstance();Singleton s2=Singleton.getInstance();Singleton s3=new Singleton();Singleton s4=new Singleton();System.out.println(s3==s4);System.out.println("=====================");System.out.println(s1==s2);System.out.println(s1.equals(s2));System.out.println("=====================");Person p1=new Person();Person p2=new Person();System.out.println(p1==p2);System.out.print(p1.equals(p2));//Image image;Dog dog=new Dog(){public void jump(){System.out.println("/nabstract");}};dog.jump();Cat cat=new Cat(){public void run(){System.out.println("/ninterfaxce");}public void jump(){System.out.println("/ninterfaxce");}};cat.jump();}}class Singleton{//private Singleton(){}private static Singleton instance;public static Singleton getInstance(){if(instance==null){instance=new Singleton();}return instance;}} class Person{//private Person(){}}abstract class Dog{public void run(){System.out.println();}abstract void jump();}interface Cat{void run();void jump();}