The Character.isJavaIdentifierStart(int codePoint) is an inbuilt method in java that determines if the character (Unicode code point) is permissible as the first character in a Java identifier. It is to be noted that a character may start 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 ‘_’).
Syntax:
public static boolean isJavaIdentifierStart(int codePoint)
Parameters: The parameter codePoint is of the integer type and refers to the character (Unicode code point) that is to be tested.
Return value: The isJavaIdentifierStart(int codePoint) method of Character class returns true if the character may start a Java identifier; false otherwise.
Below programs illustrate the Character.isJavaIdentifierStart() method:
Program 1:
// Java program to illustrate// Character.isJavaIdentifierStart() method import java.lang.*;  public class gfg {      public static void main(String[] args)    {          // Create 2 int primitives c1, c2        int c1 = 0x0039, c2 = 0x004b, c3 = 0x0081;          // Assign isJavaIdentifierPart results of         // c1, c2 to boolean primitives bool1, bool2          boolean bool1 = Character.isJavaIdentifierStart(c1);        boolean bool2 = Character.isJavaIdentifierStart(c2);        boolean bool3 = Character.isJavaIdentifierStart(c3);          String str1 = "c1 may start a Java identifier is " + bool1;        String str2 = "c2 may start a Java identifier is " + bool2;        String str3 = "c3 may start a Java identifier is " + bool3;          // Print bool1, bool2 values        System.out.println(str1);        System.out.println(str2);        System.out.println(str3);    }} |
c1 may start a Java identifier is false c2 may start a Java identifier is true c3 may start a Java identifier is false
Program 2:
// Java program to illustrate// Character.isJavaIdentifierStart() method import java.lang.*;  public class gfg {      public static void main(String[] args)    {          // Create 2 int primitives c1, c2        int c1 = 0x0034, c2 = 0x005a;          // Assign isJavaIdentifierPart results of         // c1, c2 to boolean primitives bool1, bool2          boolean bool1 = Character.isJavaIdentifierStart(c1);        boolean bool2 = Character.isJavaIdentifierStart(c2);          String str1 = "c1 may start a Java identifier is " + bool1;        String str2 = "c2 may start a Java identifier is " + bool2;          // Print bool1, bool2 values        System.out.println(str1);        System.out.println(str2);    }} |
c1 may start a Java identifier is false c2 may start a Java identifier is true
Reference: https://docs.oracle.com/javase/7/docs/api/java/lang/Character.html#isJavaIdentifierStart(char)
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