Java Strings

Creating a String

You create a String by wrapping text in double quotes and assigning it to a variable of type String. Because String is a class (not a primitive), its name begins with a capital S. Once created, the text can be printed, measured, searched, and transformed using the many methods the String class provides.

public class Main {
  public static void main(String[] args) {
    String greeting = "Hello, Java!";
    System.out.println(greeting);
  }
}

String Length

Every String can tell you how many characters it contains through the length() method. Notice the parentheses: length() is a method call for Strings, unlike arrays where length is a field without parentheses. This is a common source of confusion for beginners.

String name = "Programming";
System.out.println("Characters: " + name.length()); // 11

Common String Methods

The String class ships with dozens of helper methods. A few you will reach for constantly are shown below. Remember that these methods do not change the original String; they return a brand new one, because Strings in Java are immutable.

String title = "  java Basics  ";
System.out.println(title.trim());            // "java Basics"
System.out.println(title.trim().toUpperCase()); // "JAVA BASICS"
System.out.println("java Basics".indexOf("Basics")); // 5

• Use double quotes for String values; single quotes are only for a single char.
• length() counts every character, including spaces and punctuation.
• Chain methods left to right, for example text.trim().toLowerCase().
• To compare text, use equals() rather than == so you compare content, not object identity.