CODEWITHSUNDEEP
java
ayaz ahmad
ayaz ahmad

Reputation: 31

Simple Java Error Code while compiling

I am trying to run below code. It is giving me error

The operator + is undefined for the argument type(s) String, void

public class CompStrings{

    String s1=null;
    String s2=null;

    public void testMethod(){


        s1 = new String("Hello");
        s2 = new String("Hello");
        String str3="abc";
        String  str4 ="abc";
        /**
         * ==
         */
        if(str3==str4){
            System.out.println("str3==str4 is true");
        }else{
            System.out.println("str3==str4 is false");
        }

        if(str3.equals(str4)){
            System.out.println("str1.equals(str2) is true");
        }else{
            System.out.println("str1.equals(str2) is false");
        }

        System.out.println(s1.hashCode());
        System.out.println(s2.hashCode());

        System.out.println(s1 + " equals " + s2 + " -> " +
        s1.equals(s2));

        System.out.println(s1 + " == " + s2 + " -> " + (s1 == s2)); 
        /*Integer i1 = new Integer(10);
        Integer i2 = new Integer(10);
        System.out.println(i1.hashCode());
        System.out.println(i2.hashCode());
        1)String s1="hello";
        String s2="hello";

        2)String s1 = new String("Hello");
        String s2 = new String("Hello");

        3)String s1="hello";
        string s2=s1;

        **/

    }
    public static void main(String argv[]){
        CompStrings obj= new CompStrings();
//      \System.out.println("Calling My Method"+ obj.testMethod());

    System.out.println("Hashcode for emp1 = " + obj.testMethod());// Here it gives Error



    }


    public boolean equals(Object o){
        String s = (String) o;
        if (s1.equals(s) ){
            return true;
        }else{
            return false;
        }


        }

        public int hashCode(){
        return s1.hashCode();

        }

}

Upvotes: 3

Views: 182

Answers (6)

wannik
wannik

Reputation: 12696

testMethod() should return String instead of void.

Or, don't put the call to testMethod() inside System.out.println()

Upvotes: 0

Phil
Phil

Reputation: 3520

First, it would be more clean to write like that

String s1 = "Hello"; String s2 = "Hello";

But the problem is that testMethod() does not return a string.... it returns nothing!

Upvotes: 0

Fred
Fred

Reputation: 5006

Your obj.testMethod() return nothing (void)... so you can't concat it with a String.

Try this instead:

System.out.println("Hashcode for emp1 = ");
obj.testMethod();

Upvotes: 1

Kevin D
Kevin D

Reputation: 3594

Your testMethod() has no return type, if you wish to use it in this way it must return either a String or another Object. I say Object because all objects in Java inherit from Object, and hence will have a toString() implementation.

Upvotes: 1

Malcolm
Malcolm

Reputation: 41510

testMethod() obviously doesn't return anything, that's why there's nothing to print.

Upvotes: 4

Jon Skeet
Jon Skeet

Reputation: 1499770

testMethod() doesn't return anything - so what would you expect the result to be when you try to use the value of the expression testMethod() for any reason? (In this case you happen to be using it in string concatenation, but you couldn't assign it to a variable, pass it as an argument etc either.)

It sounds like you really want it to return a hash code, given the rest of the System.out.println call. Alternatively:

System.out.println("Calling testMethod");
obj.testMethod();
System.out.println("testMethod finished");

Upvotes: 3

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