相关疑难解决方法(0)

请使用适当的示例解释接口供应商(在Guava中)的使用.

我想在Java中实现多线程的延迟初始化.
我有一些类似的代码:

class Foo {
    private Helper helper = null;
    public Helper getHelper() {
        if (helper == null) {
            Helper h;
            synchronized(this) {
                h = helper;
                if (h == null) 
                    synchronized (this) {
                        h = new Helper();
                    } // release inner synchronization lock
                helper = h;
            } 
        }    
        return helper;
    }
    // other functions and members...
}

而且我得到了"Double-Checked Locking is Broken"声明.
我怎么解决这个问题？

我知道这个http://onjava.com/pub/a/onjava/2003/08/20/memoization.html但是还有什么吗？

懒惰的线程安全单例实例对每个编码器来说都不容易理解,所以我想在我们的企业框架中创建一个可以完成这项工作的类.

你怎么看待这件事？你觉得它有什么坏处吗？在Apache Commons中有类似的东西吗？我怎样才能让它变得更好？

Supplier.java

public interface Supplier<T> {
    public T get();
}

LazyThreadSafeInstantiator.java

public class LazyThreadSafeInstantiator<T> implements Supplier<T> {
    private final Supplier<T> instanceSupplier;

    private volatile T obj;

    public LazyThreadSafeInstantiator(Supplier<T> instanceSupplier) {
        this.instanceSupplier = instanceSupplier;
    }

    @Override
    // http://en.wikipedia.org/wiki/Double-checked_locking
    public T get() {
        T result = obj;  // Wikipedia: Note the usage of the local variable result which seems unnecessary. For some versions of the Java VM, it will make the code 25% faster and for others, it won't hurt.
        if …