Understanding Equality

[Prathyu Krishna]

why trim() doesn't output HelloWorld?

	class p
{
    public static void main(String args[])
{ 
String x= "Hello World";
String z= "Hello World".trim();
System.out.println(x.equals(z));//true
System.out.println(x);//Hello World
System.out.println(z);//Hello World
}}

[Prathyu Krishna]

Here,

String x="Hello World";
String z= "Hello World".trim();
System.out.println(x==z);//Flase

Here trim() doesn't change the value of z. Then, why it doesn't refer to the same reference as x?

[João Victor Gomes]

Prathyu Krishna wrote:

String x="Hello World";
String z= "Hello World".trim();
System.out.println(x==z);//Flase

Your code will print true. Are you sure you have compiled and run this exact code?

According to the Java API docs

Returns: A copy of this string with leading and trailing white space removed, or this string if it has no leading or trailing white space.

So, the trim() method just removes the blank spaces in the beginning and end of the String. But if the value has no changes, the trim returns the same String.

[Henry Wong]

When I run the code, I get "true" as the result.

Henry

[Prathyu Krishna]

Henry Wong wrote:
When I run the code, I get "true" as the result.

Henry

Code is from Sybex book. I didn't try to run it

[Roel De Nijs]

Prathyu Krishna wrote:Code is from Sybex book. I didn't try to run it

First of all, if you use a code snippet, a quote, a code example from another resource, you must QuoteYourSources (in your original post).

Secondly, you should pay very close attention to the actual code snippet in the book when you are trying to reproduce the output. The actual code snippet is

String x = "Hello World";
String z = " Hello World".trim();
System.out.println(x == z); // false

And although this code snippet has only 1 character more than your code snippet, it makes a very big difference!

[Roel De Nijs]

Prathyu Krishna wrote:why trim() doesn't output HelloWorld?

Honestly, that's something you can easily verify if you have a look at the javadoc of the trim() method of the String class...

[Prathyu Krishna]

I understand the trim() now, but what's the output ?
Both are Hello World, Is true the correct answer?

[Rebecca Wolf]

Prathyu Krishna wrote:I understand the trim() now, but what's the output ?
Both are Hello World, Is true the correct answer?

The best way to learn is by doing. You said you didn't run the code yet. Why didn't you? It'll help you understand the code, and you could even try different combinations to discover peculiarities and learn more. Your question would be answered in a matter of seconds.

[Roel De Nijs]

Prathyu Krishna wrote:I understand the trim() now, but what's the output ?
Both are Hello World, Is true the correct answer?

Please ShowSomeEffort!