Java – what is the difference between a = a.trim() and a.trim()?

I'm in a bit of a mess

I know that string objects are immutable This means that if I call a method from the string class, such as replace (), the original content of the string will not change Instead, a new string is returned based on the original string However, you can assign new values to the same variable

Based on this theory, I always write a = a.trim (), where a is a string Everything was fine until my teacher told me that I could also use a. trim() This messed up my theory

I tested my theory with my teacher I used the following code:

String a = "    example   ";
System.out.println(a);
a.trim();      //my teacher's code.
System.out.println(a);
a = "    example   ";
a = a.trim();  //my code.
System.out.println(a);

I get the following output:

example   
    example   
example

When I pointed it out to the teacher, she said,

Please tell me who has the right theory, because I don't know at all!

Solution

Strings are immutable in Java Trim () returns a new string, so you must get it by assignment

String a = "    example   ";
    System.out.println(a);
    a.trim();      // String trimmed.
    System.out.println(a);// still old string as it is declared.
    a = "    example   ";
    a = a.trim();  //got the returned string,Now a is new String returned ny trim()
    System.out.println(a);// new string

Edit:

Please find a new Java teacher This is a completely unsubstantiated misrepresentation