The String Methods

As mentioned, the String Class contains a large number of methods. Later, we'll see how to look up classes like String in the Official Java Documentation. I also created a String reference with example code to help beginners. However, since documentation can still be confusing for a beginner, this node will cover the most common String methods!

concatenate
Strings can be concatenated, or combined, with the + operator. For example:

String firstName = "Jim";
String lastName = "Jones";
String fullName = firstName + lastName;
System.out.println(fullName);

This will print out:

JimJones

The + operator is actually a shortcut for the concat() method. So the 3rd line in the above code can equivalently be written as:

String fullName = firstName.concat(lastName);

There's no reason to use the longer form, but you should realize + is really just concat(), an ordinary method of String.

Immutability
Unlike instances of most classes, Strings in Java are immutable, which means that a String cannot change after it has been created. Methods that look like they modify a String really just return a new String as a value. For example, the concat() method above does not change the initial String firstname, which is why a new variable fullName was needed to store the result. If you want to change the value of the current String, you can create a new String with the same variable name. For example:

String name = "Jim";
name = name.concat("Jones"); 

name now equals "JimJones".

charAt
charAt(i) - This method returns the char located at position i in the String. Strings are numbered like arrays, so the first letter in String str is at position 0, and the last letter is at position str.length()-1. For example, the following code grabs the characters 'a', 'b' and 'e':