string trim function is not working [closed]

Question

I learned string.trim() removes leading and trailing spaces. But in my case its not working i am trying below code but output is with leading and trailing space. But my expectation is text without leading and trailing space. Here is my code.

String s = " Hello Rais ";
s += " Welcome to my World ";
s.trim( );
System.out.println(s);

Please help me

Answer 1

You need to re-assign the result of trim back to s:

s = s.trim();

Remember, Strings in Java are immutable, so almost all the String class methods will create and return a new string, rather than modifying the string in place.

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Although this is off-topic, but (as I said there almost), it's worth knowing that, exception to this rule is when creating a substring of same length, or any time a method returns the string with the same value, which will be optimized and will not create a new string, but simply return this.

String s = "Rohit";
String s2 = s.substring(0, s.length());

System.out.println(s == s2); // will print true

Answer 2

In Java Strings are immutable. So s.trim() does not modify the original string but returns a new string.

String trimmed  = s.trim();

Answer 3

just add s=s.trim( ); because trim returns a new string.

Answer 4

Well..string is immutable object. so whenever you do trim(), it creates a brand new String object, which need to have a reference to access it. So do assign a reference to this trimmed String object as follows.

s = s.trim();

or

trimmedS = s.trim();

Answer 5

Understand that String in Java is immutable. Which means any operation on the String class does not change the internal string itself, but returns a new String object.

So you really need to do

s = s.trim()

which assigns the reference s to a new String object that has its trailing and leading spaces removed.

Answer 6

trim function returns a copy of the original string by trimming the white spaces so you need to store the newly returned string like s = s.trim()

From the javadocs of String#trim()

trim

public String trim()
Returns a copy of the string, with leading and trailing whitespace omitted.