Java String lines() Method

The String.lines() method in Java is used to split a string into a stream of lines. This guide will cover the method's usage, explain how it works, and provide examples to demonstrate its functionality.

Table of Contents

1. Introduction
2. lines Method Syntax
3. Examples
   • Splitting a String into Lines
   • Processing Lines in a Stream
   • Handling Empty Lines
4. Conclusion

Introduction

The String.lines() method is a member of the String class in Java, introduced in Java 11. It allows you to split a string into a stream of lines, making it easier to process multiline strings efficiently.

lines Method Syntax

The syntax for the lines method is as follows:

public Stream<String> lines()

Examples

Splitting a String into Lines

The lines method can be used to split a string into a stream of lines.

Example

import java.util.stream.Stream;

public class LinesExample {
    public static void main(String[] args) {
        String multilineString = "Hello, World!\nWelcome to Java.\nEnjoy coding!";

        Stream<String> lines = multilineString.lines();
        lines.forEach(System.out::println);
    }
}

Output:

Hello, World!
Welcome to Java.
Enjoy coding!

Processing Lines in a Stream

The lines method returns a stream, allowing you to process each line using stream operations.

Example

import java.util.stream.Stream;

public class LinesExample {
    public static void main(String[] args) {
        String multilineString = "Hello, World!\nWelcome to Java.\nEnjoy coding!";

        Stream<String> lines = multilineString.lines();
        long lineCount = lines.count();

        System.out.println("Number of lines: " + lineCount);
    }
}

Output:

Number of lines: 3

Handling Empty Lines

The lines method will include empty lines in the resulting stream.

Example

import java.util.stream.Stream;

public class LinesExample {
    public static void main(String[] args) {
        String multilineString = "Hello, World!\n\nWelcome to Java.\n\nEnjoy coding!";

        Stream<String> lines = multilineString.lines();
        lines.forEach(line -> System.out.println("Line: '" + line + "'"));
    }
}

Output:

Line: 'Hello, World!'
Line: ''
Line: 'Welcome to Java.'
Line: ''
Line: 'Enjoy coding!'

Counting Non-Empty Lines

To count only non-empty lines, you can filter out the empty lines.

Example

import java.util.stream.Stream;

public class LinesExample {
    public static void main(String[] args) {
        String multilineString = "Hello, World!\n\nWelcome to Java.\n\nEnjoy coding!";

        long nonEmptyLineCount = multilineString.lines()
                                                .filter(line -> !line.isBlank())
                                                .count();

        System.out.println("Number of non-empty lines: " + nonEmptyLineCount);
    }
}

Output:

Number of non-empty lines: 3

Conclusion

The String.lines() method in Java is used for splitting a string into a stream of lines. By understanding how to use this method, you can efficiently process multiline strings in your Java applications. Whether you are splitting a string into lines, processing each line in a stream, handling empty lines, or counting non-empty lines, the lines method provides a reliable solution for these tasks.