That is illegal syntax. It is not an optional thing for you to return a variable. You MUST return a variable of the type you specify in your method.
public String myMethod()
{
if(condition)
{
return x;
}
}
You are effectively saying, I promise any class can use this method(public) and I promise it will always return a String(String).
Then you are saying IF my condition is true I will return x. Well that is too bad, there is no IF in your promise. You promised that myMethod will ALWAYS return a String. Even if your condition is ALWAYS true the compiler has to assume that there is a possibility of it being false. Therefore you always need to put a return at the end of your non-void method outside of any conditions JUST IN CASE all of your conditions fail.
public String myMethod()
{
if(condition)
{
return x;
}
return ""; //or whatever the default behavior will be if all of your conditions fail to return.
}