Issue on Comparing String and Object value Java

Asked Nov 08 '16 at 05:32

Active Nov 08 '16 at 05:32

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I am getting one String value by using Scanner class in Java. Value stores in the field "name". I am using StringBuilder class for my logical operation and it finally stores one string value. The field name is "sb". At last, both the field holds the same value. I tried to compare the values by using .equals() and it didn't help me. Kindly refer the code on below and please help me to overcome this issue.

public static void main(String[] args) {
    System.out.println("Enter String: ");
    String name = new Scanner(System.in).nextLine();
    StringBuilder sb = new StringBuilder();
    for (int i = name.length() - 1; i >= 0; i--) {
        sb.append(name.charAt(i));
    }
    System.out.println(name);
    System.out.println(sb);
    if (name.equals(sb)) {
        System.out.println(name + " --> Palindrome");
    } else {
        System.out.println(name + " --> Not a Palindrome");
    }
}

Output:

Enter String:

madam

madam --> Not a Palindrome

asked Nov 08 '16 at 05:32

Ashok

3

`name.equals(sb.toString())`. `sb` is not a `String`, and if you compare a `String` to a non-`String` they will never be equal. – ajb Nov 08 '16 at 05:34
Thank you. It's working fine. Could you please tell me that field sb also holds "madam" right. then why we need to use .toString(). – Ashok Nov 08 '16 at 05:36
Because a `StringBuilder` is not a `String`. – shmosel Nov 08 '16 at 05:37
Because you have to compare a `String` to another `String`, and a `StringBuilder` is not a `String`. – ajb Nov 08 '16 at 05:37
Because when you pass a StringBuilder, Object's version of .equals is used instead of String's. – KC Wong Nov 08 '16 at 05:37
1

By the way, you may be interested in [`StringBuilder.reverse()`](https://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html#reverse()). – shmosel Nov 08 '16 at 05:37
1

you can use `name.contentEquals(sb)` – Saravana Nov 08 '16 at 05:38
@KCWong Technically, it's `String`'s implementation here. – shmosel Nov 08 '16 at 05:39
thanks all for support – Ashok Nov 08 '16 at 05:42

Issue on Comparing String and Object value Java

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