Java Fundamentals 3 Type conversion String Variables Cont

Java Fundamentals 3 Type conversion , String

Variables – Cont. Float The default type of floating point numbers is double. The declaration : float rate = 15. 5 f ; without the f , the compiler will generate an error 2

Variables – Cont. Char When using the char data type, you enclose each character represented within single quotations marks. Ex: char c = ‘A’ char space = ‘ ‘ Each character is represented by a value (‘A’ is represented by the value 65) char a. Charecter='A'; char a. Ascii =65; System. out. println(a. Charecter); System. out. println(a. Ascii); A A 3

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Type Conversion (Casting) Used: • to change one data type to another. • to avoid implicit type coercion. Syntax: (data. Type. Name) expression Expression evaluated first, then the value is converted to data. Type. Name Java Programming: From Problem Analysis to Program Design, Second Edition 5

Type Conversion (Casting) Examples: 1. (int)(7. 9 + 6. 7) = 14 2. (int)(7. 9) + (int)(6. 7) = 13 3. (double)(17) = 17. 0 4. (double)(7) /2 = 7. 0/2 = 3. 5 5. (double)(7/2) = 3. 0 6. (int)(7. 8+(double)(15)/2) =(int)15. 3 =15 double x=7. 9 , y= 6. 7; int result; result=(int)(7. 9 + 6. 7); Java Programming: From Problem Analysis to Program Design, Second Edition 6

Type Conversion (Casting) 8. (int)(‘A’) 9. (int)(‘ 8’) 10. (char)(65) 11. (char)(56) = 65 = 56 = ‘A’ = ‘ 8’ Java Programming: From Problem Analysis to Program Design, Second Edition 7

The class String Contains operations to manipulate strings. String: Sequence of zero or more characters. Enclosed in double quotation marks. Is processed as a single unit. Null or empty strings have no characters. “ “ Every character has a relative position , the first character is in position 0. Java Programming: From Problem Analysis to Program Design, Second Edition 8

The class String Java system automatically makes the class String available (i. e no need to import this class ) Example : Consider the following declaration : String sentence ; sentence = “programming with java” Java Programming: From Problem Analysis to Program Design, Second Edition 9

The class String Length of the string is the number of characters in it. When determining the length of a string , blanks count. Example : “ “ has length = 0 “abc” has length = 3 , position of a = 0 , b= 1 , c= 2 “a boy” has length = 5 Java Programming: From Problem Analysis to Program Design, Second Edition 10

Some Commonly Used String Methods String mystr=new String("programming with Java is fun"); System. out. println(mystr. char. At(3)); programming with Java is fun System. out. println(mystr. index. Of('J')); g System. out. println(mystr. index. Of(‘j')); 17 -1 Java Programming: From Problem Analysis to Program Design, Second Edition 11

Some Commonly Used String Methods Java Programming: From Problem Analysis to Program Design, Second Edition 12

Example String mystr=new String("programming with Java is fun"); System. out. println(mystr. index. Of('a', 10)); System. out. println(mystr. index. Of("with")); System. out. println(mystr. index. Of("ing")); programming with Java is fun 18 12 8

Some Commonly Used String Methods Java Programming: From Problem Analysis to Program Design, Second Edition 14

Examples on string methods String s 1 , s 2 , s 3 ; s 1 = “abcdefeg” ; System. out. println( s 1. length() ); // 8 System. out. println(s 1. char. At(3)); //d System. out. println(s 1. index. Of(‘e’)); //4 System. out. println(s 1. index. Of(“cd”)); //2 System. out. println(s 1. to. Upper. Case()); //ABCDEFEG Java Programming: From Problem Analysis to Program Design, Second Edition 15

Examples on string methods System. out. println(s 1. substring(1 , 4)); //bcd System. out. println(s 1 + “xyz”); // abcdefegxyz System. out. println( s 1. replace(‘d’ , ’D’)); // abc. Defeg System. out. println(s 1. char. At(4) ); // e System. out. println(s 1. index. Of(‘b’)); // 1 System. out. println(s 1. index. Of(‘e’, 5)); // 6 Java Programming: From Problem Analysis to Program Design, Second Edition 16