string printing reference in java

Question

I have this code where I am printing a string variable. The first output is showing what is expected but the second time it prints some unreadable output(I think its reference id). Please explain: Why does this happen?

public class Str3 {
    public String frontBack(String str) {
        char c[] = str.toCharArray();
        char temp = c[0];
        c[0] = c[c.length - 1];
        c[c.length - 1] = temp;
        return c.toString();
    }

    public static void main(String args[]) {
        Str3 s = new Str3();
        String s1 = new String("boy");
        System.out.println(s1);
        String s2 = s.frontBack("boy");
        System.out.println(s2);
    }
}

Output:

boy

[C@60aeb0

score 2 · Answer 1 · answered Mar 22 '14 at 05:20

2

the frontToBack() method is calling toString() on a character array object char[] which is why you see the [C@60aebo. Instead of calling toString() return with new String(c); or String.valueOf(c)

answered Mar 22 '14 at 05:20

DangerDan

519
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score 0 · Answer 2 · answered Mar 22 '14 at 05:21

0

Array types in Java do not override Object#toString(). In other words, array types inherit Object's implementation of toString() which is just

public String toString() {
    return getClass().getName() + "@" + Integer.toHexString(hashCode());
}

which is the output you see

[C@60aeb0

If you want to see a representation of the contents of an array, use Arrays.toString(..).

In your case, you seem to want to switch the first and last characters and return the corresponding string. In that case, just create a new String instance by passing the char[] to the constructor.

answered Mar 22 '14 at 05:21

Sotirios Delimanolis

274,122
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so if i want to override toString in my class can you show me , what code to ride please? – user2998784 Mar 24 '14 at 17:32
@user just write a method to do what you want it to do. – Sotirios Delimanolis Mar 24 '14 at 17:40

score 0 · Answer 3 · edited May 23 '17 at 11:51

0

You don't need to implement a custom class to do this. The functionality is already in java. This question has already been answered @ Reverse a string in Java (duplicate thread)

edited May 23 '17 at 11:51

Community

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1

answered Mar 22 '14 at 05:21

LostBalloon

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in short -> new StringBuilder(hi).reverse().toString() or for versions earlier than JDK 1.5, use java.util.StringBuffer – LostBalloon Mar 22 '14 at 05:22

score 0 · Answer 4 · answered Mar 22 '14 at 05:31

use new String(c) to c.toString();

c.toString() c mean array of chars toString() print hash method

public class Str3 {

public String frontBack(String str) {
    char c[] = str.toCharArray();

    char temp = c[0];

    c[0] = c[c.length - 1];

    c[c.length - 1] = temp;

    return new String(c);

}

public static void main(String args[]) {

    Str3 s = new Str3();

    String s1 = new String("boy");

    System.out.println(s1);

    String s2 = s.frontBack("boy");

    System.out.println(s2);

}   }

thanks for the solution...easy to understand and works!! – user2998784 Mar 24 '14 at 17:31 — user2998784, Mar 24 '14 at 17:31

string printing reference in java

4 Answers4