Using a variable that is changed within an if statement

I am writing a program in JAVA where I need to change a boolean, but I am not able to fix it.

The lay out is as follows

while(statement){
    Boolean behind = true;

    if (behind == true){
        do something
        behind = false;
        } 

    if (behind == false){
        do something else
        behind = true;
        }
}

So basically my program needs to iterate 'doing something' and 'doing something else'. But I reckon my boolean behind is not changed by the if-statement, since that 'version' of behind only lives within the statement. Any suggestions on how to cope with this?