I am using eclipse for a program, and i cannot find out why it is saying i did not initalize the variables num and denom:
if(howMany == 1)
{
if(var1 == "A")
{
num = top1;
denom = bottom;
}
if(var1 == "B")
{
num = top2;
denom = bottom;
}
System.out.print("The result is " + num + "/" + denom);
}
}
This is not the whole source, of course. I also put in
int num;
int denom;
all help appreciated!
What happens if howMay is not 1? Or if var1 is neither A nor B?
Also, use equals(), not ==, for comparing Strings.
When you post code, please use[code] and [/code] tags as described in [url=http://forum.java.sun.com/help.jspa?sec=formatting]Formatting tips[/url] on the message entry page. It makes it much easier to read.
Indeed, the compiler doesn't know whether things in an if block ever happen. So when it sees code like this:
public class Junk
{
public static void main(String[]args)
{
int a = 1;
//b is uninitialized right now
int b;
//the compiler isn't sure this if block will execute
if(a==1)
{
b=2;
}
//so it's still not sure b was initialized
// and it will tell you "variable b might not have been initialized"
System.out.println("b=" + b);
}
}
it will throw errors. If you change it to have an else that does initialize it, then it knows that either the if or the else had to execute and b must have been initialized. Like this:
public class Junk
{
public static void main(String[]args)
{
int a = 1;
//b is uninitialized right now
int b;
//the compiler isn't sure this if block will execute
if(a==1)
{
b=2;
}
else
b=3;
//COMPILER IS HAPPY NOW!
System.out.println("b=" + b);
}
}
Makes the compiler happy!
> Makes the compiler happy!
You have to be careful though. Giving it an aribtrary value just to make the compiler happy is the wrong approach. For instance, if you only allow A or B, but you get C, you should throw an IllegalArgument exception in the else case, not just assign an aribtrary value.
Or if you know there's no way to get C, then you should throw an AssertionError.
If any value is allowed, and there's a reasonable default case for all but the spcecific A or B values, then it's okay to do else { whatever = 3; } .
