Changing private final fields via reflection

Question

class WithPrivateFinalField {
    private final String s = \"I’m totally safe\";
    public String toString() {
        return \"s = \" + s;
    }
}
WithPrivateFinal         


        

Answer 1

This

class WithPrivateFinalField {
    private final String s = "I’m totally safe";
    public String toString() {
        return "s = " + s;
    }  
} 

actually compiles like this:

class WithPrivateFinalField {
    private final String s = "I’m totally safe";
    public String toString() {
        return "s = I’m totally safe";
    }  
}

That is, compile-time constants get inlined. See this question. The easiest way to avoid inlining is to declare the String like this:

private final String s = "I’m totally safe".intern();

For other types, a trivial method call does the trick:

private final int integerConstant = identity(42);
private static int identity(int number) {
    return number;
}