Android 中两种单例的写法

个人常用的有 DCL 和静态内部类实现的单例。
分别记录一下。
DCL

public class DataHelper {

private static volatile DataHelper instance;

private DataHelper() {

}

public static DataHelper getDefault() {
if (instance == null) {
synchronized (DataHelper.class) {
if (instance == null) {
instance = new DataHelper();
}
}
}
return instance;
}

}

静态内部类方式

public class DataHelper {

private DataHelper() {

}

public static DataHelper getInstance() {
return SingletonHolder.instance;
}

private static class SingletonHolder {
private static DataHelper instance = new DataHelper();
}
}