Question

Hello
What use is the final modifier on a method/constructor parameter?

Ex:

class someClass {
    private final double some; // I understand the use of final in this context, immutability etc..

    public someClass(final double some) {
        // I don't understand what purpose is served by making "some" final
        this.some = some;
    }

    public void someMethod(final double some) {
        // I don't understand what purpose is served by making "some" final
    }
}

Answer 1

There are 2 main situations when you need it:

1) you want to use the parameter inside local class (usually, anonymous class), like:

public void foo(final String str) {
    Printer p = new Printer() {
        public void print() {
            System.out.println(str);
        }
    };
    p.print();
}

2) you like the style when every variable which is not modified is marked with the final word (it is generally a good practice to keep as much things immutable as possible ).