Strings in Java

A String represents text in Java. We use strings for names, messages, file paths, and many other values. A String object is immutable: its character sequence cannot be changed after the object is created.

Why Do We Need This?

A program may trim spaces from a name, compare two messages, or build a sentence from several values. Understanding strings helps us do these tasks without confusing a new result with a change to the original object.

Main Ideas

Simple Working Example

Run this program on its own. All required imports and classes are included.

public class HelloWorld {
    public static void main(String[] args) {
        String name = "Meera";
        String greeting = "Hello, " + name;
        System.out.println(greeting);
        System.out.println(name.equals("Meera"));
        System.out.println(name.toUpperCase(java.util.Locale.ROOT));
        System.out.println(name);
    }
}

Output

Hello, Meera
true
MEERA
Meera

toUpperCase returns a result without changing name. equals compares the text. The == operator instead checks whether two references point to the same object.

Topics in This Section

• String Class
• StringBuffer
• StringBuilder
• String Methods
• Immutable vs Mutable Strings
• How many ways to create String in Java
• String Pool

Easy Way to Remember

Choose String for text values. Consider StringBuilder when building text through many changes. Choose synchronization according to how the data is shared.