Java String Methods with Examples

Strings are fundamental to most programming languages, and Java is no exception. The Java String class provides robust methods and properties for working with strings in Java code.

In this article, we will explore the ins and outs of Java strings to understand how to work with and manipulate strings efficiently in Java.

A Java string is an object that represents a sequence of characters. The String class in Java belongs to the java.lang package, so we don’t need to import it explicitly. We will examine how to create strings, what everyday operations are available, and best practices for handling strings. Mastering the Java String class is vital to writing optimized Java code for text manipulation or processing.

Creating Strings in Java

There are a few different ways to create a new Java string:

The Java String Class Constructor

We can create a string by calling the String constructor and passing a char array:

char[] myChars = {'H', 'e', 'l', 'l', 'o'};
String myString = new String(myChars);
System.out.println(myString); // Prints "Hello"

String Literals

We can also use string literals enclosed in double quotes:

String greeting = "Hello World!";

Converting Other Data Types to Strings

The String class provides methods for converting other data types like integers, floats, etc. to strings:

int age = 30;
String ageString = String.valueOf(age); 

float pi = 3.14f;
String piString = String.valueOf(pi);

Common String Operations

Example

This Java code showcases examples of some of the most commonly used String methods in Java, including charAt(), length(), indexOf(), substring(), and equals(), demonstrating their practical usage with a sample string.

public class StringMethodsExample {
    public static void main(String[] args) {
        // Define a sample string
        String text = "Hello, World!";

        // 1. charAt() - Accessing a character at a specific index
        char character = text.charAt(7);
        System.out.println("Character at index 7: " + character);

        // 2. length() - Getting the length of the string
        int length = text.length();
        System.out.println("Length of the string: " + length);

        // 3. indexOf() - Finding the position of a character or substring
        int indexOfComma = text.indexOf(",");
        System.out.println("Index of ',' in the string: " + indexOfComma);

        // 4. substring() - Extracting a substring from the original string
        String subString = text.substring(0, 5); // Extract "Hello"
        System.out.println("Substring: " + subString);

        // 5. equals() - Comparing two strings for equality
        String anotherText = "Hello, World!";
        boolean areEqual = text.equals(anotherText);
        System.out.println("Are the two strings equal? " + areEqual);
    }
}

Output:
Character at index 7: W
Length of the string: 13
Index of ‘,’ in the string: 5
Substring: Hello
Are the two strings equal? true

String Handling Best Practices

When working with Java strings, following best practices can help optimize your code:

Immutability of String Objects: String objects are immutable in Java—the value of a string cannot be changed once created, making them thread-safe. Any operation that modifies a string returns a new string object. Keep this in mind to avoid unintended reference changes.

Avoid Excessive String Concatenation: Using the + operator to concatenate strings excessively can create multiple string objects. Consider using a StringBuilder instead when programmatically generating long strings.

Use StringBuilder for Efficient String Manipulation: Methods like substring() and concat() return new string instances. For repeated string manipulations, StringBuilder is preferred over manual concatenation.

Conclusion

The Java String class provides rich methods and properties for working with strings. Its capabilities make creating, comparing, searching, extracting, replacing, and converting strings easy. Best practices, such as avoiding unnecessary String object creations, ensure optimal use of memory and CPU.

This article covered the basics of Java strings – different ways to create strings, joint string operations, and string handling best practices. The String class is fundamental to Java programming, and mastering it will help you write more efficient code that works with text.