Why does this function not work?

Programming Questions

kodereakt..

Why does this function not work?

in Programming Questions • 2 years ago

Hi all. I know I'm probably doing something really stupid and just can't see it.

float pMass(String type) {
if(type == "DIRT") {
    return 3.5;
}
if(type == "SAND") {
    return 3.5;
}
if(type == "ROCK") {
    return 5.0;
}
}

pMass is being called as such:

pMass(pType[foo])

It refuses to run with the reason "This method must return a result of type float."
The pType array is definately full. I know it is because I use it elsewhere without problem.
What am I not doing right?

Replies(6)

atze123

Re: Why does this function not work?

2 years ago

Because it doesn't return anything if String type isn't DIRT, SAND or ROCK.

The best way to do this is with switch:

float pMass(String type)
{
switch(type)
{
case "DIRT":
return 3.5;
case "SAND":
return 3.5;
case "ROCK":
return 5.0;
default: // This will happen if its nothing
return 0.0; // of the three choices above
}
}

but you also can do it by writing easily

else {
return 0.0;
}

at the end ;)

PhiLho

Re: Re: Why does this function not work?

2 years ago

Uh? In Java 1.6, you cannot switch on strings!

andreas.s..

Re: Why does this function not work?

2 years ago

in case none of your if statements are true, the function does not know what to return. add for example

return -1;

at the end of your function.

by default -1 will then be returned if no match was found before.

(update: atze123 was a tiny bit faster :) )

kodereakt..

Re: Why does this function not work?

2 years ago

That's great! Thanks guys!

bustup

Re: Why does this function not work?

2 years ago

Suprised no one said it before, but when comparing strings in Java 1.6+ you have to use equals.

if (type.equals("DIRT"))

A simple way to demonstrate why "==" doesn't always work is

String s1 = "foobar";
String s2 = "foobar";
// this will print
if (s1 == s2) System.out.println("s1 and s2 are ==");

This will print "s1 and s2 are ==".

String s1 = "foobar";
// fool the compiler just a bit
String s3 = "foo";
s3 = s3 + "bar";
if (s1 == s3)
System.out.println("s1 and s3 are ==");
else
System.out.println("s1 and s3 ARE NOT ==");

And this will print "s1 and s3 ARE NOT ==".

PhiLho

Re: Why does this function not work?

2 years ago

I didn't mention it because there was chances it was working if using the strings defined in the same sketch, as you shown. But you are right to mention the issue. The issue can also arise if getting the strings from a file, too.

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