Java - 函数没有返回我的预期

Question

Here's the code:

import java.util.*;

public class HelloWorld
{

public static void main(String[] args)
{
    String string1 = "randomString1";                       
    System.out.print(f(string1));
}

public static int f(String string)
{
    try { 
        String string2 = "randomString2";

        if(string.equals(string2) == true);
            return 0;
    }
    catch(Exception e){
        e.printStackTrace();
    }

    return 1;
}

}//end of class

Now, the output of this program is

0

But I expected it to be:

1

Because what I wanted the f function to do was to return 0 if the strings were the same and 1 if they weren't.

So, there's definitely something I know wrong here, and I'm guessing it has something to do with the equals method.

Answer 1

this is the problem:

if(string.equals(string2) == true);
----------------------------------^

you'll need remove the semi-colon else, it is pretty much an expression on its own doing nothing:

if(string.equals(string2) == true) return 0;

Answer 2

if(string.equals(string2) == true); you have a semicolon there which does not belong. Honestly you don't even need the == true part as well.

Answer 3

because of the semi-colon in the end of your if :

if (string.equals(string2) == true);
//---------------------------------^
return 0;

So when you make a semi-colon in the end of if mean that a statement is end start a new statement which is return 0 for that you get 0 and not 1

to understand more, what did you have mean this :

if (string.equals(string2) == true){
   //do nothing
}
//pass to the next statement
return 0;

So instead you can use :

if (string.equals(string2)){
   return 0;
}

Answer 4

man...

if(string.equals(string2) == true);

The semi-colon (;) this prevents the code to go inside the if block, and hence the

return 0; 

line executes and returns 0

The program works fine as it should.

The solution to your problem...

if(string.equals(string2))
    return 0;

Remove the semi-colon.. the code would work fine.

Answer 5

You have an unnecessary semilocon at the end of your if statement. Try below option:

if(string.equals(string2)) {
     return 0;
}

Answer 6

Simplified.

public static int f(String string)
{
    String string2 = "randomString2";

    return (!TextUtils.isEmpty(string) && string.equals(string2)) ? 0 : 1;
}

No need of try-catch as TextUtils will handle null for string.