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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

// 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:

Java

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

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

// 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

// 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)

Character.isIdentifierIgnorable() in Java with Examples

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