Java Scanner next() vs nextLine() methods: What's the difference?

What’s the difference between next() and nextline()?

The difference between the Java Scanner’s next() and nextLine() methods is that nextLine() will return every character in a line of text, right up until the carriage return, while next() will split the line up into individual words, returning individual text Strings one at a time.

Imagine someone passed the following phrase into a Java Scanner:

next vs nextline example in Java

Sample text for the next versus nextLine example.

Calls to next() and nextLine()

In this case, the first call to next() would return a single word:

Programmers

In contrast to next(), nextLine() returns all of the text in a single line of input, right up to the first line break.

If the sample text above was passed to a Scanner and the nextLine() method was called, the output would be:

Programmers love Java!

Unlike next(), nextLine() will return an entire line of text, right up to the first line break.

next vs nextLine Java Scanner

This next vs nextLine example shows the difference between the two Java Scanner methods.

Scanner next() vs nextLine() comparison

The following chart compares what the Java Scanners next() and nextLine() methods would return on four subsequent calls of the following sample text:

Programmers love Java! 
User input with Java is so easy! 
Just use the Scanner class. 
Or maybe the Console or JOptionPane?
next() vs nextLine() processing of sample text
Iteration next() method output nextLine() method output
 First iteration
 Programmers
 Programmers love Java!
 Second iteration
 love
 User input with Java is so easy!
 Third iteration
 Java!
 Just use the Scanner class.
 Fourth iteration
 User
 Or maybe the Console or JOptionPane?

Java next() vs nextLine() example

As with any concept in Java, the best way to solidify your understanding of the difference between the next() and nextLine() methods is to actually write some code.

Code the following next() versus nextLine() example yourself and compare how the two Scanner methods are different:

package com.mcnz.nextLine.example;
import java.util.*;

public class NextVersusNextLine {

  public static void main(String[] args) {

    String sampleText = 
        " Programmers love Java!\n"
      + " User input with Java is so easy!\n"
      + " Just use the Scanner class.\n"
      + " Or maybe the Console or JOptionPane?\n";

    Scanner scanner = new Scanner(sampleText);

    System.out.println("First call : " + scanner.nextLine());
    System.out.println("Second call: " + scanner.nextLine());
    System.out.println("Third call : " + scanner.next());
    System.out.println("Fourth call: " + scanner.next());

    scanner.close();

  }
}

When this code runs, the output is:

First call : Programmers love Java!
Second call: User input with Java is so easy!
Third call : Just
Fourth call: use

As you can see, the call to nextLine() will print out an entire line of text, right up to the end of the line, while next() will only print out a single word at at a time.

Delimiters and String tokenization

When the Java Scanner’s next() method breaks a line of text up into individual words, that’s known as tokenization.

By default, the next() method creates a new token each time it sees whitespace. The character that triggers tokenization is known as a delimiter.

The Scanner class allows you to change the delimiter to any valid text String. So if you wanted to tokenize text based on colons instead of whitespace, you’d just create the Java Scanner like this:

Scanner s = new Scanner("How:now:brown:cow!").useDelimiter(":");

Scanner next() vs nextLine explained

To summarize the key points to remember when the differences between next() and nextLine() are compared, remember these important points:

  1. The nextLine() method returns all text up to a line break
  2. The next() method returns tokenized text
  3. The next() method uses whitespace as the default delimiter
  4. The delimiter of the next() method can be changed to any valid String

With these key points in mind, you shouldn’t have any difficulty understanding the difference between the Java Scanner’s next() and nextLine() methods.

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