Question

在我最初设计的后面的《法典》中,“批号”需要在整个申请执行过程中发出下一个增益值。因此,我把这个班子变成一个单一州。然而,随着最近一些要求的变化,我需要重新确定“批号”。我只是添加了这样做的重新定点方法。然而,这无疑违反了单一州的模式,我也知道,以这种方式启动固定成员并不是一个好的想法。

你认为我应该做些什么?

public final class GetNextNumber {
    private static GetNextNumber instance; 
    private static Integer nextNumber=1;
    private GetNextNumber() {
    }
    public static synchronized GetNextNumber getInstance() {
        if(instance==null){
            instance = new GetNextNumber();
        }
        return instance;
    } 
    protected Integer getNextNumber(){
        return nextNumber++;
    }
    protected synchronized void reset(){
        nextNumber=1;
    }
    public Object clone() throws CloneNotSupportedException {
        throw new CloneNotSupportedException();
    }
}

Answer 1

为什么没有田地就是一个例子变量? 这里无需静态。

重新设定的一定要同步进行,除非获得NextNumber。

Answer 2

看一下科索沃,除两点外:

getNextNumber is not synchronized.
since getNextNumber and reset are not static, nextNumber doesn t need to be static, either.

您可使用rel=“nofollow”>AtomicInteger>,以避免出现和reset >:code>

public final class GetNextNumber {

    private static GetNextNumber instance;

    private AtomicInteger nextNumber = new AtomicInteger(1);

    private GetNextNumber() {
    }

    public static synchronized GetNextNumber getInstance() {
        if(instance==null){
            instance = new GetNextNumber();
        }
        return instance;
    } 

    protected Integer getNextNumber(){
        return nextNumber.getAndIncrement();
    }

    protected void reset(){
        nextNumber.set(1);
    }
}

关于这方面的进一步讨论,见http://www.javamex.com/tutorials/synchronization_concurrency_7_atomic_integer_long.shtml”rel=“nofollow>。 Java5级原子学:原子学和原子学::

Before Java 5, we had to write classes with access to the counter variable in synchronized blocks or methods, or else use a volatile variable which is a lighter form of synchronization but with the risk that some updates could be missed if they happen concurrently. An AtomicInteger can be used as a drop-in replacement that provides the best of both worlds...

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