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1,提前初始化
public class Singleton {
private static Singleton instance = new Singleton();
private Singleton() {
}public static Singleton getInstance() {
return instance;
}
}
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2.双重检查锁定 + volatile。
public class Singleton {
private static volatile Singleton instance;private Singleton() {
}public static Singleton getInstance() {
if (instance == null) {
synchronized (Singleton.class) {
if (instance == null) {
instance = new Singleton();
}
}
}
return instance;
}
}
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3.延迟初始化占位类模式。
public class Singleton {
private static class InstanceHolder {
public static Singleton instance = new Singleton();
}private Singleton() {
}public static Singleton getInstance() {
return InstanceHolder.instance;
}
}
