android單例模式怎么實現

在Android中，可以通過以下幾種方式實現單例模式：

1. 懶漢式

public class Singleton {
private static Singleton instance;
private Singleton() {}
public static synchronized Singleton getInstance() {
if (instance == null) {
instance = new Singleton();
}
return instance;
}
}

2. 餓漢式

public class Singleton {
private static final Singleton instance = new Singleton();
private Singleton() {}
public static Singleton getInstance() {
return instance;
}
}

3. 雙重檢查鎖定

public class Singleton {
private volatile static Singleton instance;
private Singleton() {}
public static Singleton getInstance() {
if (instance == null) {
synchronized (Singleton.class) {
if (instance == null) {
instance = new Singleton();
}
}
}
return instance;
}
}

4. 靜態內部類

public class Singleton {
private static class SingletonHolder {
private static final Singleton INSTANCE = new Singleton();
}
private Singleton() {}
public static Singleton getInstance() {
return SingletonHolder.INSTANCE;
}
}

以上是幾種常見的Android中實現單例模式的方式，具體選擇哪種方式取決于實際需求和性能要求。