Check the character type

static boolean isDefined(char ch)
if a character is defined in Unicode.
static boolean isDigit(char ch)
if the character is a digit.
static boolean isHighSurrogate(char ch)
if the char is a high-surrogate code unit.
static boolean isIdentifierIgnorable(char ch)
if the character should be regarded as an ignorable character in a Java identifier or a Unicode identifier.
static boolean isISOControl(char ch)
if the character is an ISO control character.
static boolean isJavaIdentifierPart(char ch)
if the character may be part of a Java identifier as other than the first character.
static boolean isJavaIdentifierStart(char ch)
if the character is permissible as the first character in a Java identifier.
static boolean isLetter(char ch)
if the character is a letter.
static boolean isLetterOrDigit(char ch)
if the character is a letter or digit.
static boolean isLowerCase(char ch)
if the character is a lowercase character.
static boolean isLowSurrogate(char ch)
if the char value is a low-surrogate code unit.
static boolean isMirrored(char ch)
whether the character is mirrored according to the Unicode specification.
static boolean isSpaceChar(char ch)
if the character is a Unicode space character.
static boolean isSurrogatePair(char high, char low)
whether the pair of char values is a valid surrogate pair.
static boolean isTitleCase(char ch)
if the character is a titlecase character.
static boolean isUnicodeIdentifierPart(char ch)
if the character may be part of a Unicode identifier as other than the first character.
static boolean isUnicodeIdentifierStart(char ch)
if the character is permissible as the first character in a Unicode identifier.
static boolean isUpperCase(char ch)
if the character is an uppercase character.
static boolean isWhitespace(char ch)
if the character is white space according to Java.

public class Main{
  public static void main(String[] argv){
    System.out.println("is digit:"+Character.isDigit('a'));    
    System.out.println("is letter:"+Character.isLetter('a'));    
    System.out.println("is lowercase:"+Character.isLowerCase('a'));    
    System.out.println("is space char:"+Character.isSpaceChar('a'));    
    System.out.println("is white space:"+Character.isWhitespace('a'));    
    System.out.println("is upper case:"+Character.isUpperCase('a'));    
    System.out.println("is Java identifier start:"+Character.isJavaIdentifierStart('a'));    

  }
}

The output:


is digit:false
is letter:true
is lowercase:true
is space char:false
is white space:false
is upper case:false
is Java identifier start:true

The following code uses a for loop to check the each value in a char array.


  public class Main {
  public static void main(String args[]) {
    char a[] = {'J', 'a', 'v', 'A', '2', '.','c','O','M'};

    for (int i = 0; i < a.length; i++) {
      if (Character.isDigit(a[i]))
        System.out.println(a[i] + " is a digit.");
      if (Character.isLetter(a[i]))
        System.out.println(a[i] + " is a letter.");
      if (Character.isWhitespace(a[i]))
        System.out.println(a[i] + " is whitespace.");
      if (Character.isUpperCase(a[i]))
        System.out.println(a[i] + " is uppercase.");
      if (Character.isLowerCase(a[i]))
        System.out.println(a[i] + " is lowercase.");
    }
  }
}
  

The output:


J is a letter.
J is uppercase.
a is a letter.
a is lowercase.
v is a letter.
v is lowercase.
A is a letter.
A is uppercase.
2 is a digit.
c is a letter.
c is lowercase.
O is a letter.
O is uppercase.
M is a letter.
M is uppercase.
Home 
  Java Book 
    Essential Classes  

Character:
  1. Create a character object from char value
  2. Get char value from Character object
  3. Check the character type
  4. Get the char type from char value
  5. Change character case
  6. Compare two characters
  7. Convert character to String
  8. Get the numeric value for a char