java语句顺序有时非常重要

我们学习java时，通常被告知，变量定义的顺序不重要，可是下面程序确在jdk 1.7上执行出错。

public class FactoryImpl implements Serializable {
    private final static  FactoryImpl INSTANCE = new FactoryImpl();
    private final static AtomicInteger count = new AtomicInteger(0);

    private int id;

    private FactoryImpl() {
        id = count.incrementAndGet();
    }

    public int getId() {
        return id;
    }

    public static FactoryImpl getInstance() {
        return INSTANCE;
    }

    public static void main(String[] args) {
        FactoryImpl impl1 = FactoryImpl.getInstance();
        System.out.println(impl1.id);
    }
}

把下面代码调整顺序之后能够运行成功。

    private static final FactoryImpl INSTANCE = new FactoryImpl();
    private final static AtomicInteger count = new AtomicInteger(0);