Oct 08, 2023
浅谈单例
写在前头：希望你了解到的不仅是模式，而学会用OOP的眼光分析问题，解决问题。
静态单例
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12//最简单的单例，静态单例，在第一次调用get_instance时对象已经创建
public class Singleton {
//kc：创建静态对象
private static Singleton instance = new Singleton();
//kc:构造函数私有
private Singleton() {}
public static Singleton getInstance() {
System.out.println("this is a call without create!");
return instance;
}
}延时加载单例(线程不安全)
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17//延迟创建对象，第一次调用get_instance时才创建对象，线程不安全
public class delay_single {
public static delay_single instance;
private delay_single() {}
public static delay_single getInstance() {
//此处线程不安全
if(instance==null) {
instance= new delay_single();
System.out.println("this is a create call!");
}
System.out.println("this is a call");
return instance;
}
}延时加载单例(线程安全)
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14//延迟创建，与delay_single的差别在于，引入了synchronized，线程安全
public class delay_singleton2 {
public static delay_singleton2 instance;
private delay_singleton2() {}
//synchronized关键字，保证线程安全
public static synchronized delay_singleton2 getInstance() {
if(instance==null) {
instance= new delay_singleton2();
}
return instance;
}
}