Java char value and its attributes

In this chapter you will learn:

How to Check the value of a character type
How to Get the char type from char value
How to Change character case
How to compare two characters

Check the value of a character type

A char type value can store a letter or a digit. The letter can be upper case or lower case. It can also store unicode. The following list of methods are the ones we are going to use to check the char type value.

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

A demo for some of the methods listed above.

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'));    
/*j a  va  2s . c om*/
  }
}

The output:

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[] = {'D', 'e', 'm', 'O', '2', '.','c','O','M'};
/* j ava 2  s. 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:

D is a letter./*from j  av a  2  s . co m*/
D is uppercase.
e is a letter.
e is lowercase.
m is a letter.
m is lowercase.
O is a letter.
O 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.

Get the char type from char value

static int getType(char ch) returns a value indicating a character's general category.

public class Main{
  public static void main(String[] argv){
    System.out.println(Character.getType('a'));    
/*  j av a 2  s  .  c  o  m*/
  }
}

The output:

Change character case

static char toTitleCase(char ch) converts to titlecase.
static char toUpperCase(char ch) converts to uppercase.
static char toLowerCase(char ch) converts to lowercase.

public class Main{
  public static void main(String[] argv){
    System.out.println(Character.toTitleCase('a'));    
    System.out.println(Character.toUpperCase('a'));    
    System.out.println(Character.toLowerCase('a'));    
/*from j a  va 2  s . c om*/
  }
}

The output:

Compare two characters

int compareTo(Character anotherCharacter) compares two Character objects numerically.
boolean equals(Object obj) compares this object against the specified object.

public class Main {
  public static void main(String[] argv) {
    Character character1 = new Character('a');
    Character character2 = new Character('b');
    System.out.println(character1.compareTo(character2));
  }//  j a va2  s.  c  om
}

The output:

Next chapter...

What you will learn in the next chapter:

Home » Java Tutorial » Data Types

Java Primitive Data Types

Java byte type

Java byte type conversion

Java short type

Java short type conversion

Java int type

Java int type conversion

Java long type

Java long type conversion

Java float type

Java float type conversion

Java double type

Java double type creation and comparison

Java double type conversion