What does $ mean in java?

The $ symbol in Java is used in anonymous inner classes to access local variables or parameters of the outer class: $outerVar: access local variables of the outer class. $outerParam: Access parameters of external classes.

The meaning of $ in Java

$ in Java is usually used to represent local variables in anonymous inner classes or parameters.

Anonymous inner class

An anonymous inner class is an inner class without a name that is defined directly in the context in which it is created. The syntax is as follows:

new SuperClass() {
    // 匿名内部类的成员
};

$ Function

In an anonymous inner class, the $ symbol is used to access local variables or parameters of the outer class. It means that local variables or parameters in the outer class are available in the anonymous inner class.

Example

class OuterClass {
    int outerVar = 5;

    void outerMethod() {
        int outerParam = 6;
        new Thread(() -> {
            // $outerVar 可以访问外部类的局部变量 outerVar
            System.out.println("$outerVar: " + $outerVar);
            // $outerParam 可以访问外部类的参数 outerParam
            System.out.println("$outerParam: " + $outerParam);
        }).start();
    }
}

It should be noted that the

• $ symbol can only be used in anonymous inner classes , it has no special meaning in other contexts. The
• $ symbol can only be used to access local variables or parameters of an external class, but cannot be used to access methods or fields of an external class.
• If there are multiple local variables or parameters with the same name in the outer class, you need to use explicit qualifiers (such as this.$outerVar) to specify the variables to be accessed.

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