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					Package and Some Classes


   Declaration of Package
   Usage of Package
   Package of Java Language
      What is Package ?

   Way to group a related class and interface into
    one unit
   To resolve the name conflicts between class
    names
      Declaration of Package

            package PackageName ;


   Declare at the beginning of source file
          [Print1.java], [Print2.java]


                          MyTest


                          Prints


           Print1.class              Print2.class
        Usage of Package

   Use of absolute path name
       Declare to describe the full package name
       To resolve conflicts between class names


         MyTest.Prints.Print1 m1;
         MyTest.Prints.Print2 m2;


            [AbsolutePath.java]
        Use of import Statement

        import packageName.className ;


   Include all the classes in package
       import packageName.*;

        import MyTest.Prints.*;


            [ImportTest.java]
          java.lang Package

   Basic class to enlarge the function of Java

   Provide classes according to primitive type
    (wrapper class)
       Integer class, Double class,. ..
          java.lang Class

                             Object
Wrapper Class

           Number                              System
                         Character          String
Integer

          Long                 Boolean   StringBuffer

                 Float

                         Double
             Object Class
   Super class of all classes
   All classes are to inherit the methods of Object class
   Method
       Object clone() : To copy the object equally
       boolean equals(Object obj) :
            Compare the object as parameter with the object which calls this method
       int hashCode() : Calculate the hash code value of the object
       Class getClass() : To get Class object corresponding to object
       String toString() : Convert the object into string
             [Ex 8.5]
       wait(), notify() : To control the status of thread
          Wrapper Class

 Classes correspond to primitive type
 int -> Integer, char -> Character, double -> Double


   Reasons
       Role of home for constants and methods for each type
       When we need to deal with primitive type as object
        Number Class

 Abstract Class
 Super Class of Integer, Long, Float, Double

   Method
       abstract int intValue() : Convert into int type
       abstract long longValue() : Convert into long type
       abstract float floatValue() : Convert into float type
       abstract double doubleValue() : Convert into double type
             Integer Class
   Constant
       public static final int MAX_VALUE = 2147483647
       public static final int MIN_VALUE = -2147483648
   Method
       static int parseInt(String s) :
            Convert a Number in String into int type
       static int parseInt(String s , int radix) :
            Convert a number in String into int type with radix
       static String toBinaryString(int i) :
            Convert into binary string form
       static String toHexString(int i) :
            Convert into hexadecimal string form
   Interger Class

        [IntegerClass.java]


Interger.parseInt(s);          As it is static
Interger.toBinaryString(i);     method...
...
          Double Class

   Constant
       public static final double MAX_VALUE
        =1.79769313486231570e+308
       public static final double MIN_VALUE =
        4.94065645841246544e-308
       public static final double NaN = 0.0 / 0.0
       public static final double NEGATIVE_INFINITY = -1.0 / 0.0
       public static final double POSITIVE_INFINITY = 1.0 / 0.0
        Double Class

   the parameter is NaN or not.
       static boolean isInfinite(double v) :
            Check whether the parameter is infinite or not.
       static Double valueOf(String s) : Method
       static long doubleToLongBits(double value) :
            Convert the bits represented by double type into long type bit
             pattern
       static boolean isNaN(double v) :
          Check whether
          Convert String into Double type
        Boolean Class

   Constant
       public static final Boolean TRUE = new Boolean(true)
       public static final Boolean FALSE = new Boolean(false)
   Method
       Boolean(boolean b) :
            Constructor to create boolean object receiving the initial value b
       Boolean(String s) :
            Constructor to receive the string value "true“ or "false“
       boolean booleanValue() :
            Return the boolean value of object
       static boolean getBoolean(String name) :
            Return the boolean value of system attribute
       static Boolean valueOf(String s) :
            Return the Boolean value correspond to string s
        Character Class
   Constant
       public static final int MAX_RADIX = 36
       public static final char MAX_VALUE =‘\ffff’
       public static final int MIN_RADIX = 2
       public static final char MIN_VALUE =’\0000’

   Method
       Character(char value) : Constructor to initialize the object as value
       char charValue() : Convert into char type
       static boolean isDigit(char ch) : Test whether is digit?
       static boolean isLetter(char ch) : Test whether is letter?
       static boolean isLetterOrDigit(char ch) : Return when it is letter or
        digit.

            [CharacterClass.java]
        String Class
   Method
       char charAt(int index) :
            Return the character at specific position in string
       int length() :
            Return the length of string
       String toUpperCase() :
            Convert the string into upper character
       String toLowerCase() :
            Convert the string into lower character
       String trim() :
            Remove the white space before/after string
       String substring(int beginIndex) :
            Make the sub string from beginIndex to the end of the string
        StringBuffer Class

 Provide the string sequence operation
 Method
       StringBuffer append(Type obj) :
            Append the obj(to be changed into string) to string
       StringBuffer insert(int offset, Type obj) :
            Insert obj(to be changed into string) into specified position


             Object         String           char[]
             boolean        char             int
             long           float            double
 StringBuffer Class


String now = new java.util.Date().toString();
StringBuffer strbuf = new StringBuffer(now);
strbuf.append(" : ").append(now.length).append('.');
System.out.println(strbuf.toString());
        System Class

   Class for Java Virtual Machine and the control and
    security for OS system
   Define the standard input and output
   Field
      public static InputStream in :
            Stream to read data from standard input device
       public static PrintStream out :
            Stream to output data to standard output device
       public static PrintStream err :
            Standard Error Stream to output error message

				
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