为什么Javac抱怨未初始化变量? [英] Why does javac complain about not initialized variable?

问题描述

对于此Java代码:

String var;
clazz.doSomething(var);

为什么编译器会报告此错误:

Why does the compiler report this error:

变量'var'可能尚未初始化

Variable 'var' might not have been initialized

我认为所有变量或引用都被初始化为 null .为什么需要这样做:

I thought all variables or references were initialized to null. Why do you need to do:

String var = null;

??

推荐答案

实例和类变量初始化为null(或0)，而局部变量不初始化.

Instance and class variables are initialized to null (or 0), but local variables are not.

请参见§4.12.5 JLS 的详细说明基本上是一样的东西:

See §4.12.5 of the JLS for a very detailed explanation which says basically the same thing:

程序中的每个变量都必须有一个值，然后才能使用它的值:

Every variable in a program must have a value before its value is used:

• 每个类变量，实例变量或数组组件在创建时均使用默认值初始化:
  • [从所有默认值的清单中剔除]

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