java split strings function

Question

I'm trying to build a program which reads a certain String after using the Split function

import java.util.Scanner;

   public class Lexa2 {

public void doit() {
    String str = "( 5 + 4 ) * 2";
    String [] temp = null;
    temp = str.split(" "); 
    dump(temp);
}
public void dump(String []s) {
    for (int i = 0 ; i < s.length ; i++) {           
        if (s[i] == "(") {              
            System.out.println("This is the left paren");
        } else if (s[i] == ")"){                
            System.out.println("This is the right paren");          
        }else  if (s[i] == "+"){                
            System.out.println("This is the add");          
        }else  if (s[i] == "-"){                
            System.out.println("This is the sub");          
        }else  if (s[i] == "*"){                
            System.out.println("This is the mult");         
        }else  if (s[i] == "/"){                
            System.out.println("This is the div");          
        }else               
            System.out.println("This is a number");
    }
}   

     public static void main(String args[]) throws Exception{
       Lexa2 ss = new Lexa2();
         ss.doit();
 }
    }

The output should be something like this:

This is the left paren
this is a number
this is the add
this is the right paren
this is a number

**DON'T USE == FOR STRING COMPARISON** I say it loudly because it has been repated so many times in a softer voice, maybe you need it. — Marko Topolnik, May 11 '12 at 10:13
[15.21 Equality Operators](http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.21) — hmjd, May 11 '12 at 10:16
possible duplicate of [Java String.equals versus ==](http://stackoverflow.com/questions/767372/java-string-equals-versus) — Marko Topolnik, May 11 '12 at 10:21

score 4 · Answer 1 · answered May 11 '12 at 10:16

4

you're pretty close, just replace (s[i] == "?") with (s[i].equals("?"))

answered May 11 '12 at 10:16

pstanton

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Thanks i always mess up with the lamest mistakes :) – Lu Yas May 11 '12 at 10:27

Alberto Solano · Answer 2 · 2012-05-12T09:41:54.803

1

Don't use s[i] == ")" to compare strings. In this way, you're not checking if the string in s[i] is equal to ).

Use the equals method. Then you can compare the strings using:

if (s[i].equals("("))

Replace equals in the other if statements.

UPDATE

P.S. I think the best way to compare strings, looking to your code, is to use the switch/case statements. But, this feature is only available in Java 7. I think this will avoid the continuous checking with if statements, and the code will be more readable. If you have Java 7, use this feature, otherwise, in case of Java 6 or lower, follow @pstanton suggestion. ;-)

edited May 12 '12 at 09:41

answered May 11 '12 at 10:23

Alberto Solano

7,972
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1

switches don't work with strings, so he/she would need to use char – pstanton May 12 '12 at 01:50
@pstanton You're right, indeed this feature is available only in Java 7. Thank you :-) Answer updated! For further info, take a look to: http://stackoverflow.com/questions/338206/switch-statement-with-strings-in-java – Alberto Solano May 12 '12 at 09:43

java split strings function

2 Answers2