can some one plz explain me the difference between these two things..
what is the difference betwn equals () and ==?
why do they show diffenett result while applyin on object references ..

equals() compares the object's contents (deep comparison)
== compares the reference values (shallow comparison)

- A.Kahtava

thanks Adam..again one problem with --how to override equals () and hashcode() method..i never come to know how would they be implemented?
plz help me with this topic..also if u have any links , then plz do send them..
regards,
praveena

Best example :-

public class Str
{
    public static void main(String args[])
    {
        String s1 = "hello";

        String s2 = "hello";

        String s3 = new String("hello");

        String s4 = new String("hello");

    System.out.println("s1==s2\t" + (s1==s2));
    System.out.println("s1==s3\t" + (s1==s3));
    System.out.println("s3==s4\t" + (s3==s4));

System.out.println("s1.equals(s2)\t" + (s1.equals(s2)));
System.out.println("s1.equals(s3)\t" + (s1.equals(s3)));
System.out.println("s3.equals(s4)\t" + (s3.equals(s4)));
    }
}

the == and equals are different
String s1="Malli";
String s2="Malli";
if(s1==s2) it fails because it compare the address only not content
if(s2.equals(s1)) it compares the content

K.Mallikarjunarao

Hi Malli,

i think you're mistaken, the s1==s2 will return true, as adam has mentioned its a shallow comparision it compares references, the s1 and s2 will point to the same reference, and the equals() method will return true.

Regards,
Rakesh

== operator work only primitive data types
primitive data types are such as int,long,byte,double,float etc
equals operator work for reference only
such as Integer,Double,Float

K.Mallikarjunarao

Dear Mallikarjun

according to the above discussion both of u r right and perhaps u would like to have a look at the snippet mentioned in http://java.sun.com/docs/books/tutor...datatypes.html
This would tell u the special importance given to java.lang.String

You can read through these lines mentioned
In addition to the eight primitive data types listed above, the Java programming language also provides special support for character strings via the java.lang.String class. Enclosing your character string within double quotes will automatically create a new String object; for example, String s = "this is a string";. String objects are immutable, which means that once created, their values cannot be changed. The String class is not technically a primitive data type, but considering the special support given to it by the language, you'll probably tend to think of it as such.

Thanks & Regards
     vinay