Page 1 : Library Classe,, , , , " Distinction between primitive data type and composite data type © Introduction to, wrapper Classes © Methods of wrapper classes and their usage with respect to Numeric, and character data types viz.: int parselnt(String s), long float and double type o Boolean, isDigit(chay ch) © Boolean isLetter(char ch) © Boolean isLowerCase(char ch) o Boolean, isUpperCase(char ch) © Boolean isWhitespace(char ch) © char toLowerCase(char ch), © char LoUpperCase(char ch) © Autoboxing and Unboxing wrapper classes, , , , Java Development Kit JDK) 1.5 includes all types of software tools which are essential},, needed while writing programs, The major component of JDK 1.5 is Java Class Libr,, , (ICL) that contains various packages. Each package of JCL is a collection of Classes, containing different built-in functions. There are numerous packages available in JCL,, Some important packages which are frequently used in Java programming are liste, , below:, , , , ary, Java.lang Contains classes related to string manipulations., java.io Contains classes for input/output operations., javaawt Contains classes to implement Graphical User Interface., java.util Contains utility classes to implement data structure., Java.applet Contains classes for implementing applets., java.net Contains classes for supporting network operations., Java.math Contains classes for mathematical operations., Note:, ; The keyword ‘import’ is used to ' ha b cae he int eine, include a package in a Java program. can be used in the program. In case,, Syntax: import <package name,*>; you want to use only a specific class, ¢.g., import java.io. *; of a package then use the class name, , in place of asterisk sign (*)., , For example: import java.util.Scanner;, 2. java.lang is a package that is imported, , by default to any Java program., , import java.util. *:, , 138 | Understanding Computer Applications with BlueJ—X
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tive data type and Composite daiy fype, ve data types are the fundamental OV basic A., Fem developers. These data fypes are de, 1 ingle element (number or character), as ., , For example: int, float, char, double, ete,, , i Vygis o/bich ate created by the, SHEN 1 de Nare a variable that Can Contain, , ver. ring roger ' Peas, , However durin Under ae DIMMIVe types are not wf ways sitticient to handle, complex c Ms u retuled ; auch Circumstances, 4 group of sinilar oF different primitive, = one referen o i gl A specific data type, 1 is kraut as nom-primitive, or compose ¢ ce data type, Array is a compute data type that uses similar, type of primitive data,, Java Ete the user 10 create a data type hy including a set of primitive, data types. J oe oo by using a class, When a class io defined, it becomes a data type, for the user. Here, class contains 4 number of primitive data types which is referred to, as a ‘User Defined Data Type! or ‘Composite Data Type", Shus, the class name can be, used to declare any variable (object) in our programm,, , Difference hetween Primitive and ¢ Lomposite Data Types, Compose Data Type, J, It is a fundamental data type, 1, It is a 4et Of primitive data types., , 9, Primitive data types are defined by the 2, Composite data types are defined by the, system developers. USFS,, , Now, let us discuss a built-in data type that is composite in nature and is referred to, as Wrapper class., , Wrapper Class, , Java language uses wrapper classes that are, a part of Java library package java.lang, The, wrapper class is a class that contains a primitive, data type. Whenever an object to a wrapper, class is created, a field in memory is allocated, to contain a primitive data., , ‘Integer’ is a wrapper class that contains, primitive data type ‘int’ and the following, functions:, , * Integer.parseInt( ): To convert a string into integer data type., , * Integer.toString( ): To convert an integer data type into string., , The tag ‘Integer’ used along with the functions signifies that the functions belong to, , Integer wrapper class., , , , Need of Using Wrapper Classes, Basically, wrapper classes contain primit, Classes in Java serve two primary purposes:, , * To store primitive values in the objects., , * To convert a string data into other primitive types and vice-versa., , ive date values in terms of objects. The wrapper
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F, , (b) float variable=Float.valueOf(String);, e.g., float n; String s= “24,35” ,, n=Float.parseFloat(s);, or, , n=Float.valucOf(s);, Thus, the variable n results in 24,35 (without quotes), , . String to Double type data, Syntax:, (a) double variable=Double.parseDouble(String);, (b) double variable=Double.valucOf(String);, e.g., double n; String s= “24,315467398";, n=Double.parseDouble(s);, or, n=Double.valueOf(s);, , Thus, the variable n results in 24.315467398 (without quotes)., , Note: (i, , The conversion from string to primitive type data is possible when it, contains only numbers. If you try these functions with alphabetic or alphanumeric String then it throws NumberFormatException. It must be kept, in mind that valueOf( ) function is available in Java 1.5 or higher version., Hence, to run valueOf() function, your computer system must have Java, version JDK 1.5 or more., , Conversion from Primitive type data to String, A primitive type data can also be converted into String type. The process is illustrated, below:, * Integer type data to String type, Syntax: String variable=Integer.toString(int);, e.g., int n=24; String s;, s=Integer.toString(n);, Here, an integer type number (n=24) gets con, Hence, s= “24”., Now, you can’t perfo, , verted to a String., , rm any mathematical operations with the variable *s’,, , * Long type data to String type, , Syntax: String variable=Long.toString(long);, eg., long n=246935; String $;, , s=Long.toString(n);, Here, a long type number (n, Hence, s= “246935”., , =246935) gets converted to a String., , Library Classes | 141
