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shabbir 6Jul2014 18:02

Essential Java.lang Classes
 
Java.lang package contains the classes that are fundamental to the design of the Java programming language.

Java.lang.Character Class



The java.lang.Character class wraps a value of the primitive type char in an object. An object of type Character contains a single field whose type is char.

Class declaration
Code:

public final class Character
  extends Object
      implements Serializable, Comparable<Character>

Class constructors
  • Character(char value) - Newly allocated Character object is created which represents the specified char value.
Class methods
  1. static int charCount(int codePoint) - It returns the number of char values needed to represent the specified character.
  2. static int codePointAt(char[] a, int index) - Code point at the given index of the char array is returned.
  3. static int codePointAt(CharSequence seq, int index) - Code point at the given index of the CharSequence is returned.
  4. int compareTo(Character anotherCharacter) - Two Character objects are compared numerically.
  5. static int getNumericValue(char ch) - The int value represented by the specified Unicode character is returned.
  6. static boolean isLowerCase(char ch) - Determines whether the specified character is a lowercase character or not.
  7. static boolean isUpperCase(char ch) - Determines whether the specified character is an uppercase character or not.
  8. static boolean isWhitespace(char ch) - Determines whether the specified character is white space according to Java.
  9. static char toLowerCase(char ch) - Character argument is converted to lowercase using case mapping information from the UnicodeData file.
  10. String toString() - String object representing this Character's value is returned.
  11. static char toUpperCase(char ch) - Character argument is converted to uppercase using case mapping information from the UnicodeData file.
  12. static Character valueOf(char c) - Character instance representing the specified char value is returned.
Example
Code:

public class CharacterDemo {
      public static void main(String[] args) {
      Character c1, c2;
      c1 = new Character('v');
      c2 = new Character('d');
      int result;
//  compares c2 with c1
    result = c1.compareTo(c2);
      if( result == 0 ){
              System.out.println("Both charcters are equal.");
      }
      else if( result > 0 ){
              System.out.println("First character is greater than Second.");
      }
      else if( result < 0 ){
              System.out.println("Second character is greaterthan First.");
      }
  }
}

Output

http://imgs.g4estatic.com/java/java-.../Character.png

Java.lang.Float Class



The java.lang.Float class wraps a value of primitive type float in an object. An object of type float contains a single field whose type is float.

Class declaration
Code:

public final class Float
  extends Number
    implements Comparable<Float>

Class constructors
  1. Float(double value) - Creates a new float object which represents the argument converted to type float.
  2. Float(float value) - Creates a new float object which represents the primitive float argument.
  3. Float(String s) - Creates a new float object which represents the floating-point value of type float represented by the string.
Class methods
  1. static int compare(float f1, float f2) - Two specified float values are compared for equality
  2. double doubleValue() - Double value of the Float object is returned.
  3. float floatValue() - Float value of the Float object is returned.
  4. int intValue() - Value of the Float as an int is returned (by casting to type int).
  5. long longValue() - Value of the Float as a long is returned (by casting to type long).
  6. static float parseFloat(String s) - This method returns a new float initialized to the value represented by the specified string.
  7. short shortValue() - Value of this Float as a short is returned (by casting to a short).
  8. String toString() - String representation of this Float object is returned.
  9. static Float valueOf(float f) - Float instance representing the specified float value is returned.
  10. static Float valueOf(String s) - Float object holding the float value represented by the argument string is returned.
Example
Code:

class FloatDemo
{
        public static void main(String dt[])
        {        float a,b;
                double mul=0;
                try{
                        a= Float.parseFloat(dt[0]);
                        b= Float.parseFloat(dt[1]);
                        mul= a*b;
                        System.out.println("Result is="+mul);
                }
                catch (NumberFormatException e)
                {        System.out.println(e);
                }
                catch (ArithmeticException e)
                {        System.out.println(e);
                }
                catch(ArrayIndexOutOfBoundsException e)
                {        System.out.println(e);
                }
                catch(Exception e)
                {        System.out.println(e);
                }
                finally
                {        System.out.println("Thank you");
                }
        }
}

Output

http://imgs.g4estatic.com/java/java-...sses/Float.png

Java.lang.Integer Class



The java.lang.Integer class wraps a value of the primitive type int in an object. An object of type Integer contains a single field of int type.

Class declaration
Code:

public final class Integer
  extends Number
    implements Comparable<Integer>

Class constructors
  1. Integer(int value) - Newly allocated Integer object is constructed which represents the specified int value.
  2. Integer(String s) - Newly allocated Integer object is constructed which represents the int value indicated by the string parameter.
Class methods
  1. double doubleValue() - Value of this Integer is returned as a double.
  2. float floatValue() - Value of this Integer is returned as a float.
  3. static Integer getInteger(String nm) - Integer value of the system property with the specified name is determined.
  4. int intValue() - Value of this Integer is returned as int.
  5. long longValue() - Value of this Integer is returned as a long.
  6. static int parseInt(String s) - The string argument is parsed as a signed decimal integer.
  7. String toString() - String object is returned representing this Integer's value.
  8. static String toString(int i) - String object is returned representing the specified integer.
  9. static Integer valueOf(int i) - Integer instance is returned representing the specified int value.
  10. static Integer valueOf(String s) - Integer object is returned holding the value of the specified String.
Example
Code:

class ExceptionDemo
{
        public static void main(String dt[])
        {
                int a,b, div=0;
                try
                {
                        a= Integer.parseInt(dt[0]);
                        b= Integer.parseInt(dt[1]);
                        div= a/b;
                        System.out.println("div is="+div);
                }
                catch (NumberFormatException e)
                {
                        System.out.println(e);
                }
                catch (ArithmeticException e)
                {
                        System.out.println(e);
                }
                catch(ArrayIndexOutOfBoundsException e)
                {
                        System.out.println(e);
                }
                catch(Exception e)
                {
                        System.out.println(e);
                }
                finally
                {
                        System.out.println("Thank you");
                }
        }
}

Output

http://imgs.g4estatic.com/java/java-...es/Integer.png


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