String buffer in java

Question

import java.lang.*;
class hello
{
    public static void main(String args[])
    {
         StringBuffer s3 = new StringBuffer("R");
         String s1 = "Rahul";
         char ch = s1.charAt(0);
         System.out.println(s3.toString().equals(ch));
    }
}

Output should be TRUE but it is showing false. Please help.

@Juvanis: It compiles as per String.equals(Object param) and autoboxing of char to Character. param is not limited to String. — Steph
– Steph, Commented Mar 31, 2013 at 8:57

Denys Séguret · Accepted Answer · 2013-03-31 08:59:41Z

4

Most ovverridings of equals don't return true if the types aren't the same.

String's equals implementation is like this :

1012    public boolean equals(Object anObject) {
1013        if (this == anObject) {
1014            return true;
1015        }
1016        if (anObject instanceof String) {
               ...
1030        }
1031        return false;
1032    }

Here, you're comparing a String and a Character (due to autoboxing, as an Object is needed).

What you can do is ensure you're comparing a string to a string :

    System.out.println(s3.toString().equals(""+ch));

or simply compare the characters, as you know ch is a character :

    System.out.println(s3.charAt(0)==ch);

edited Mar 31, 2013 at 8:59

answered Mar 31, 2013 at 8:53

Denys Séguret

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Comments

Steph · Accepted Answer · 2013-03-31 08:53:52Z

1

It is not related to StringBuffer, it is because you compare th String "R" to the char 'R'

answered Mar 31, 2013 at 8:53

Steph

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Howard · Accepted Answer · 2013-03-31 08:54:46Z

1

You are comparing the string "R" to the character 'R' which according to Java isn't equal, because the types do not match.

answered Mar 31, 2013 at 8:54

Howard

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Comments

Vishal K · Accepted Answer · 2013-03-31 09:22:56Z

0

You are checking equality between a String (s2.toString()) and a Character (ch) . So, it is returning false . For equality check you should first typecase that char to String . You can use the following code:

System.out.println(s3.toString().equals(String.valueOf(ch)));

edited Mar 31, 2013 at 9:22

answered Mar 31, 2013 at 8:58

Vishal K

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