net.gdface.utils.ILazyInitVariable Maven / Gradle / Ivy
package net.gdface.utils;
import java.util.concurrent.atomic.AtomicReference;
/**
* 延迟初始化(Lazy initialization)变量封装接口
* @author guyadong
*
* @param 延迟变量类型
*/
public interface ILazyInitVariable {
/**
* 返回延迟初始化的 T 实例
* @return T 实例
*/
public T get();
public static abstract class BaseLazyVar implements ILazyInitVariable{
/**
* 返回 T 实例
* @return T 实例
*/
abstract protected T doGet() ;
}
/**
* @since 2.9.9
*/
public abstract class VolatileVar extends BaseLazyVar{
private volatile V var = null;
protected abstract V in( T t);
protected abstract T out(V var);
@Override
public T get() {
// Double-checked locking
if(null == var){
synchronized(this){
if(null == var){
var = in(doGet());
}
}
}
return out(var);
}
}
/**
* 使用{@link AtomicReference}对变量进行封装，确保值为{@code null}时也只初始化一次
* @since 2.9.9
*/
public static abstract class VolatileReferenceVar extends VolatileVar>{
/**
* 返回不为{@code null}的实例，确保{@link #doGet()}方法只会执行一次
*/
@Override
protected final AtomicReference in(T t) {
return new AtomicReference<>(t);
}
@Override
protected final T out(AtomicReference var) {
return var.get();
}
}
}