什么是RIWO（读取间接写出）状态 [英] What is RIWO (Read Indirectly Write Out) state

问题描述

我正在阅读关于静态流量控制的内容并且遇到了RIWO概念。有人可以用简单的术语和代码样本解释这个吗？

I was reading about the static flow control and came across the RIWO concept. Can someone explain this with simple terminology and perhaps a code sample?

这与错误非法转发参考有关。

This is related to the error "Illegal forward reference".

相关链接。

推荐答案

在浏览了一些材料并与几个人离线讨论后，我发现了以下信息。

After going through some material and discussing with couple of guys offline i found out the following information.

当java类被执行时，JVM按顺序执行几个步骤的步骤很少。

When a java class is getting executed there are few steps which JVM performs few steps sequentially.

• 从上到下识别静态成员。


• 从上到下执行静态变量赋值和静态块。


• 执行main方法。

在这些阶段中，有一个名为RIWO（只读间接写入）的静态变量状态。

During these phases there is one such state called RIWO(Read Indirectly Write Only) for a static variable.

期间RIWO变量无法通过其引用直接访问。相反，我们需要使用间接方式来调用某些变量。

During RIWO a variable cannot be accessed directly with its reference. Instead we need to use an indirect way to call certain variables.

例如：

class Riwo
{
 static int i = 10;
 static
 {
  System.out.println(i);
 }
 }

在上述情况下，输出为10.

In the above case the output is 10.

class Riwo {
static int i = 10;
static {
    m1();
    System.out.println("block1");
}

public static void main(String... args) {
    m1();
    System.out.println("block main");
}

public static void m1() {
    System.out.println(j);
    System.out.println("block m1");
}

static int j = 20;
static {
    System.out.println("end of code");
}
}

在上述情况下，输出为

0
block m1
block1
代码结束
20
block m1
block main

0 block m1 block1 end of code 20 block m1 block main

class Riwo
{
static
{
    System.out.println(i);
    System.out.println("block1");
}
static int i = 10;
public static void main(String... args)
{
    System.out.println("main block");
}
}

在上面的例子中，我们得到以下编译时错误

In the above case we get the following compile time error

Riwo.java:5：非法转发参考
System.out.println（i）;

Riwo.java:5: illegal forward reference System.out.println(i);

这意味着当它处于RIWO状态时我们无法直接读取静态变量。我们应该使用方法间接调用变量。

That means we cannot read a static variable directly when it is in RIWO state.We should call the variable indirectly using a method.

这篇关于什么是RIWO（读取间接写出）状态的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！