Java Scanner hasNext() Method with Example

Scanner Class hasNext() method: Here, we are going to learn about the hasNext() method of Scanner Class with its syntax and example.
Submitted by Preeti Jain, on March 26, 2020

Scanner Class hasNext() method

Syntax:

    public boolean hasNext();
    public boolean hasNext(Pattern patt);
    public boolean hasNext(String patt);

hasNext() method is available in java.util package.
hasNext() method is used to check whether this Scanner has any other token exists in its input or not.
hasNext(Pattern patt) method is used to check whether the next complete token meets the given pattern or not.
hasNext(String patt) method is used to check whether the next complete token meets the pattern (patt) formed from the given string.
These methods may throw an exception at the time of checking the given pattern.
IllegalStateException: This exception may throw when this Scanner is not opened.
These are non-static methods, it is accessible with class object & if we try to access these methods with the class name then we will get an error.

Parameter(s):

In the first case, hasNext(),
- It does not accept any parameter.
In the second case, hasNext(Pattern patt),
- Pattern patt – represents the pattern to read.
In the second case, hasNext(String patt),
- String patt – represents this string to denotes the pattern to read.

Return value:

In all the cases, the return type of the method is boolean,

In the first case, it returns true when this Scanner has any other token in its input exists otherwise it returns false.
In the second and third case, it returns true when this Scanner has any other token exists meet the given pattern (patt).

Example:

// Java program is to demonstrate the example
// of hasNext() method of Scanner

import java.util.*;
import java.util.regex.*;

public class HasNext {
 public static void main(String[] args) {
  String str = "Java Programming! 3 * 8= 24";

  // Instantiates Scanner
  Scanner sc = new Scanner(str);

  // By using hasNext() method is to
  // check whether this object has more
  // token or not
  boolean status = sc.hasNext();
  System.out.println("sc.hasNext(): " + status);

  // By using hasNext(Pattern) method is to
  // check whether the given pattern exists
  // in this object or not
  status = sc.hasNext(Pattern.compile("...a"));
  System.out.println("sc.hasNext(Pattern.compile(...a)): " + status);

  // By using hasNext(String) method is to
  // check whether the given pattern exists
  // formed from the given string or not
  status = sc.hasNext("..0.a");
  System.out.println("sc.hasNext(..0.a): " + status);

  // Scanner closed
  sc.close();
 }
}

Output

sc.hasNext(): true
sc.hasNext(Pattern.compile(...a)): true
sc.hasNext(..0.a): false

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