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:

   
   

   
   
   

   // 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 );    } }
   Output:

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

   Program 2:

   
   

   
   
   

   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 );    } }
   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:

   
   

   
   
   

   // 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);    } }
   Output:

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

   Program 2:

   
   

   
   
   

   // 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);    } }
   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)