kotlin实现

}

java实现

public class LazyNotThreadSafe {
    private static LazyNotThreadSafe INSTANCE;
    private LazyNotThreadSafe(){}
    public static LazyNotThreadSafe getInstance(){
        if(INSTANCE == null){
            INSTANCE = new LazyNotThreadSafe();
        }
        return INSTANCE;
    }
}

java实现

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

kotlin实现

class LazyThreadSafeSynchronized private constructor() {
    companion object {
       private var instance: LazyThreadSafeSynchronized? = null
        @Synchronized
        fun get(): LazyThreadSafeSynchronized{
            if(instance == null) instance = LazyThreadSafeSynchronized()
            return instance!!
        }
    }
}

kotlin实现

class LazyThreadSafeDoubleCheck private constructor(){
    companion object{
        val instance by lazy(mode = LazyThreadSafetyMode.SYNCHRONIZED){
            LazyThreadSafeDoubleCheck()
        }
        private @Volatile var instance2: LazyThreadSafeDoubleCheck? = null
            if(instance2 == null){
                synchronized(this){
                    if(instance2 == null)
                        instance2 = LazyThreadSafeDoubleCheck()
                }
            }
            return instance2!!
        }
    }
}

java实现

public class LazyThreadSafeStaticInnerClass {
    private static class Holder{
        private static LazyThreadSafeStaticInnerClass INSTANCE = new LazyThreadSafeStaticInnerClass();
    }
    private LazyThreadSafeStaticInnerClass(){}
    public static LazyThreadSafeStaticInnerClass getInstance(){
        return Holder.INSTANCE;
}