Character.isIdentifierIgnorable() in Java with Examples

  1. The java.lang.Character.isIdentifierIgnorable(char ch) is an inbuilt method in java that determines if the specified character should be regarded as an ignorable character in a Java identifier or a Unicode identifier.

    The following Unicode characters are ignorable in a Java identifier or a Unicode identifier:

    • ISO control characters that are not whitespace
      1. ‘\u0000’ through ‘\u0008’
      2. ‘\u000E’ through ‘\u001B’
      3. ‘\u007F’ through ‘\u009F’
    • all characters that have the FORMAT general category value

    Syntax:

    public static boolean isIdentifierIgnorable(char ch)

    Parameters: The parameter ch is of character datatype and refers to the character that is to be tested.

    Return Value: This method returns true if the character is an ignorable control character that may be part of a Java or Unicode identifier, false otherwise.



    Below programs illustrate the Character.isIdentifierIgnorable(char ch) method:

    Program 1:

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    // Java program to illustrate
    // Character.isIdentifierIgnorable(char ch) method
    import java.lang.*;
      
    public class gfg {
      
       public static void main(String[] args) {
      
          // Creates 2 character primitives c1, c2 and assigning values
          char c1='\u0000', c2= '9';
      
          // Assigns isIdentifierIgnorable results of 
          // c1, c2 to boolean primitives
          boolean  bool1 = Character.isIdentifierIgnorable(c1);
          boolean  bool2 = Character.isIdentifierIgnorable(c2);
      
          String str1 = "c1 is an ignorable control character is " + bool1;
          String str2 = "c2 is an ignorable control character is " + bool2;
      
          System.out.println( str1 );
          System.out.println( str2 );
       }
    }

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    Output:

    c1 is an ignorable control character is true
    c2 is an ignorable control character is false
    

    Program 2:

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    import java.lang.*;
      
    public class gfg {
      
       public static void main(String[] args) {
      
          // Create 2 character primitives c1, c2 and assigning values
          char c1='\u000E', c2= '8';
      
          // Assigns isIdentifierIgnorable results of 
          // c1, c2 to boolean primitives
          boolean  bool1 = Character.isIdentifierIgnorable(c1);
          boolean  bool2 = Character.isIdentifierIgnorable(c2);
      
          String str1 = "c1 is an ignorable control character is " + bool1;
          String str2 = "c2 is an ignorable control character is " + bool2;
      
          System.out.println( str1 );
          System.out.println( str2 );
       }
    }

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    Output:

    c1 is an ignorable control character is true
    c2 is an ignorable control character is false
    
  2. The java.lang.Character.isIdentifierIgnorable(int codePoint) is similar to the previous method in all manner.

    Syntax:

    public static boolean isIdentifierIgnorable(int codePoint)
    

    Parameter: The function accepts a single parameter codePoint of integer datatype which specifies the character (Unicode code point) that is to be tested.

    Return value: This method returns true if the character is an ignorable control character that may be part of a Java or Unicode identifier, false otherwise.

    Below program illustrates the Character.isIdentifierIgnorable(int codepoint) method:
    Program 1:

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    // Java program to demonstrate 
    // the Character.isIdentifierIgnorable(int codepoint) method
      
    import java.lang.*;
      
    public class gfg {
      
       public static void main(String[] args) {
      
          // Integer primitives c1, c2
          int c1 = 0x019f, c2 = 0x1abc;
      
          // Assign isIdentifierIgnorable results of cp1, cp2
          // to boolean primitives bool1, bool2
         boolean bool1 = Character.isIdentifierIgnorable(c1);
         boolean bool2 = Character.isIdentifierIgnorable(c2);
      
          // Print bool1, bool2 values
          System.out.println( "c1 is an ignorable control character?"+
          " ans is "+bool1);
          System.out.println( "c2 is an ignorable control character?"+
          " ans is "+bool2);
       }
    }

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    Output:

    c1 is an ignorable control character? ans is false
    c2 is an ignorable control character? ans is false
    

    Program 2:

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    // Java program to demonstrate 
    // the Character.isIdentifierIgnorable(int codepoint) method
      
    import java.lang.*;
      
    public class gfg {
      
       public static void main(String[] args) {
      
          // Integer primitives c1, c2
          int c1 = 0x119f, c2 = 0x0abc;
      
          // Assign isIdentifierIgnorable results of cp1, cp2
          // to boolean primitives bool1, bool2
         boolean bool1 = Character.isIdentifierIgnorable(c1);
         boolean bool2 = Character.isIdentifierIgnorable(c2);
      
          // Print bool1, bool2 values
          System.out.println( "c1 is an ignorable control character?"+
          " ans is "+bool1);
          System.out.println( "c2 is an ignorable control character?"+
          " ans is "+bool2);
       }
    }

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    Output:

    c1 is an ignorable control character? ans is false
    c2 is an ignorable control character? ans is false
    

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

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