java 多例_Java 单例及多例

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一、单例的作用是用于控制类的生成方式，而不让外部类任意new对象

1.Car.java

import java.util.ArrayList;

import java.util.List;

public class Car {

//私有化构造函数，防止被外部的类new

private Car() {

}

private static Car car = new Car();//单例

private static List cars = new ArrayList();//多例，类似连接池

public static Car getInstance() {

return car;

}

public void run() {

System.out.println("Car running...............");

}

}

2.Test.java

public class Test {

@org.junit.Test

public void test() {

Car car = Car.getInstance();

car.run();

Car car2 = Car.getInstance();

System.out.println(car == car2);

System.out.println(car.equals(car2));

}

}

运行结果：

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