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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