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32 lines
723 B
32 lines
723 B
2 years ago
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### 1.内部静态类
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内部静态类即使存在多个类加载器的情况下也只会初始化一次，因此是线程安全的
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```java
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public class StaticHolderSingleton {
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private StaticHolderSingleton() {
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}
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private static class ClassHolder {
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static final StaticHolderSingleton INSTANCE = new StaticHolderSingleton();
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}
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public static StaticHolderSingleton getInstance() {
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return ClassHolder.INSTANCE;
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}
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public static void main(String[] args) {
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StaticHolderSingleton clz = StaticHolderSingleton.getInstance();
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}
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}
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```
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### 2.基于枚举
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```java
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public enum EnumSingleton {
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INSTANCE;
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EnumSingleton() {
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}
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}
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```
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当EnumSingleton.INSTANCE首次被引用时才会被初始化
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