Comments on: Java String comparison. The difference between == and equals().

By: Erinyes

Erinyes — Mon, 30 Jan 2012 14:07:18 +0000

Wow, I never knew that _this_ is the difference between both compare operations. Thanks for the info! Much appreciated

By: sandesh

sandesh — Thu, 26 Jan 2012 10:05:01 +0000

thanx a lot ……… i was breaking my head as i did the same mistake of confusing == ……..
your article helped ………

By: Leo Nardus

Leo Nardus — Wed, 23 Nov 2011 20:40:33 +0000

Hi .. Thanks mate for your posting ..
It’s help me a lot ..
Love it ..

By: Praveen

Praveen — Wed, 16 Nov 2011 11:47:29 +0000

Before reding your post i had confision to use these operators. Now i got clear idea. Thanks for your post..

By: Pajarito

Pajarito — Fri, 21 Oct 2011 11:18:05 +0000

So, what is the diff between:

String a = “abc”;
String a = new String(“abc”);

Beacuse “everything in Java is an object” the first one above is an object of String class, the same as the latter. Is there any difference?

By: Nascar

Nascar — Sat, 01 Oct 2011 07:02:10 +0000

Or can we say?
If (!month.equals(“J”, “F”,“A”)) {
Perform error validation;
}

By: Nascar

Nascar — Sat, 01 Oct 2011 06:28:09 +0000

Hi,

Thanks for the post. I am just a beginner in Java.

I need to know how to validate multiple values for a string.
like, if the value of month is not equal to J or F or M, perform some error handling.
The requirement is: J, F and M are the expected (good) values for month.

Example: If (!month.equals(“J”) || !month.equals(“F”) || !month.equals(“A”)) {
Perform error validation;
}

Is the above correct?

Any help is appreciated. Thanks

By: Robert

Robert — Fri, 30 Sep 2011 19:07:37 +0000

Ok, the equals() method makes sense, but what if you cant use the == or <= to compare a variable? How do you use equals() to test a range of values, assuming you can at all?

By: Tom N.

Tom N. — Mon, 26 Sep 2011 20:22:40 +0000

I haven’t looked at the Java source code, but my educated guess is that the Java run time is placing all the constant strings (i.e. “abc”) at specific locations in memory, and then assigning the pointers (i.e. s1) to point to those locations. Both of the “abc” constants, being equal, would (as a optimization) be assigned to the same location, Since s1 was assigned to point to that location, s1 == “abc” will be true. If you built up the string “abc” in another fashion, this would not be the case,

Tom

By: Naveen

Naveen — Mon, 26 Sep 2011 13:28:14 +0000

String s1=”abc”;

if(s1==”abc”){
System.out.println(“Both are Equal”);
}else{

System.out.println(“Both are not Equal”);
}

Output:- Both are Equal

How this can Happen can any one please explain ?