Java substring not working

问题

Forgive me, I'm new to Java and have an extremely basic question. I have a string and want a substring of it, for example:

String str = "hello";
str.substring(1);
System.out.println(str);

Instead of getting "ello" I get the original "hello", any idea why this is? Thanks.

回答1:

Strings cannot be changed in Java, so you will need to re-assign the substring as such:

str = str.substring(1)

as opposed to calling the method by itself.

回答2:

Strings in Java are immutable. I believe you want to do this:

String str = "hello";
str = str.substring(1);
System.out.println(str);

回答3:

You aren't saving the changes done on the string.

str=str.substring(1);

回答4:

You need to save the substring into a new variable (or the old one if you prefer). Something like this should do the trick:

String str = "hello";
String strSub = str.substring(1);
System.out.println(strSub);

For people reading this post, remember that substring(1) means take the substring starting at char 1 and going until the end of the string.

回答5:

You can directly put it in the .println(..)

String str = "hello";
System.out.println(str.substring(1));

but str will remain unchanged.

来源：https://stackoverflow.com/questions/11130422/java-substring-not-working