构造函数内的初始化块

发布于 2024-11-19 05:22:20 字数 602 浏览 2 评论 0原文

我知道初始化块在构造函数中调用“super()”之后运行。然而，今天早上查看一些代码时，我发现了以下内容：

public class SimpleListLocalsAnalysis extends BackwardFlowAnalysis
    FlowSet emptySet;

    public SimpleLiveLocalsAnalysis(UnitGraph graph) {
        super(graph);

        {
            Chain locals = g.getBody().getLocals();
            FlowUniverse localUniverse = new FlowUniverse(locals.toArray());
            emptySet = new ArrayPackedSet(localUniverse);
        }

        doAnalysis();
    }
...
}

上面的代码显示了“super(graph)”调用之后初始化块内正在进行的一些初始化。将代码放在构造函数内的初始化块中的目的是什么，因为它肯定会在调用 super 之后运行。我在这里错过了什么吗？

原文

I know that an initialization block runs after the call to 'super()' in a constructor. However, when looking through some code this morning, I found the following:

public class SimpleListLocalsAnalysis extends BackwardFlowAnalysis
    FlowSet emptySet;

    public SimpleLiveLocalsAnalysis(UnitGraph graph) {
        super(graph);

        {
            Chain locals = g.getBody().getLocals();
            FlowUniverse localUniverse = new FlowUniverse(locals.toArray());
            emptySet = new ArrayPackedSet(localUniverse);
        }

        doAnalysis();
    }
...
}

The above code shows some initialisation going on within an initialisation block just after 'super(graph)' invocation. What's the purpose of placing the code in an initialisation block within a constructor, as surely it runs anyway after the call to super. Am I missing something here?

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む无字情书 2024-11-26 05:22:20

它不是初始化块，它的简单块

就像

public void foo(){

  {
      //some code
  }
}

目的：

你可以限制范围

Its not initilization block, its simple block

just like

public void foo(){

  {
      //some code
  }
}

Purpose:

You can have restricted scope

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等风也等你 2024-11-26 05:22:20

找出答案的最好方法可能是询问代码的作者。也许他包围了代码块以表明这些初始化的重要性。或者他这样做可能是因为他想表明 locals 和 localUniverse 仅用于初始化 emptySet。

另一方面，在 Java 中，您可以执行类似的操作，

public class SomeClass extend ParenClass{
    private int val;   

    {
        //initializztion block
        val = -1;
    }

    public SomeClass()
    {
        super();
    }

    public SomeClass(String iniName)
    {
        super(iniName);
    }   
}

初始化块将在编译时复制到每个构造函数的开头（在 super 调用之后）。

所以也许作者将代码块复制并粘贴到了错误的地方；他将其复制到构造函数中而不是构造函数外部。

The best way to find out is probably to ask the author of the code. Maybe he surrounded the block of code to indicate the importance of those initialization. Or maybe he did that because he wants to show that locals and localUniverse are only used for initializing emptySet.

On the other hand, in Java you can do something like

public class SomeClass extend ParenClass{
    private int val;   

    {
        //initializztion block
        val = -1;
    }

    public SomeClass()
    {
        super();
    }

    public SomeClass(String iniName)
    {
        super(iniName);
    }   
}

The initialization block will get copy to the beginning of each of the constructors (after the super call) during compile time.

So maybe the author copy and pasted the block of code into wrong place; he copied it into the constructor instead of outside of the constructor.

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