Character.isJavaIdentifierStart() method in Java

The java.lang.Character.isJavaIdentifierStart(char ch) is an inbuilt method in java which determines if the specified character is permissible as the first character in a Java identifier or not. A character may start as a Java identifier if and only if one of the following conditions is true:

  • isLetter(ch) returns true
  • getType(ch) returns LETTER_NUMBER
  • ch is a currency symbol (such as ‘$’)
  • ch is a connecting punctuation character (such as ‘_’).

Note: This method cannot handle supplementary characters. To support all Unicode characters, including supplementary characters, use the isJavaIdentifierStart(int) method.

Syntax:

public static boolean isJavaIdentifierStart(char ch)

Parameters: The function accepts one mandatory parameter ch which specifies the character to be tested.

Return value: This method returns a boolean value. The boolean value is True if the character may start a Java identifier, False otherwise.



Program below demonstrates the Character.isJavaIdentifierStart(char ch) method:

Program 1:

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java program to demonstrate the
// Character.isJavaIdentifierStart()
import java.lang.*;
  
public class gfg {
  
    public static void main(String[] args)
    {
  
        // create 2 char primitives c1, c2
        char c1 = '9', c2 = '-';
  
        // assign isJavaIdentifierStart results of c1, c2
        // to boolean primitives  bool1, bool2
        boolean bool1 = Character.isJavaIdentifierStart(c1);
        System.out.println(c1 + " may start a Java identifier is : " + bool1);
  
        boolean bool2 = Character.isJavaIdentifierStart(c2);
        System.out.println(c2 + " may start a Java identifier is : " + bool2);
    }
}

chevron_right


Output:

9 may start a Java identifier is : false
- may start a Java identifier is : false

Program 2:

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java program to demonstrate the
// Character.isJavaIdentifierStart()
  
import java.lang.*;
  
public class gfg {
  
    public static void main(String[] args)
    {
  
        // create 2 char primitives c1, c2
        char c1 = '5', c2 = '_';
  
        // assign isJavaIdentifierStart results of c1, c2
        // to boolean primitives  bool1, bool2
        boolean bool1 = Character.isJavaIdentifierStart(c1);
        System.out.println(c1 + " may start a Java identifier is : " + bool1);
  
        boolean bool2 = Character.isJavaIdentifierStart(c2);
        System.out.println(c2 + " may start a Java identifier is : " + bool2);
    }
}

chevron_right


Output:

5 may start a Java identifier is : false
_ may start a Java identifier is : true

Reference: https://docs.oracle.com/javase/7/docs/api/java/lang/Character.html#isJavaIdentifierStart(char)

Attention reader! Don’t stop learning now. Get hold of all the important Java and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready.




My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.