1 / 27

Chapter 2 – Continued Basic Elements of Java

Chapter 2 – Continued Basic Elements of Java. Chapter Objectives. Type Conversion String Class Commonly Used String Methods Parsing Numeric Strings Commonly Used Escape Sequences. Type Conversion (Casting). Used: to change one data type to another . to avoid implicit type coercion.

joann
Download Presentation

Chapter 2 – Continued Basic Elements of Java

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 2 – Continued Basic Elements of Java

  2. Chapter Objectives • Type Conversion • String Class • Commonly Used String Methods • Parsing Numeric Strings • Commonly Used Escape Sequences

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

  4. Type Conversion (Casting) Examples: (int)(7.9 + 6.7) = 14 (int)(7.9) + (int)(6.7) = 13 (double)(17) = 17.0 (double)(8+3) = (double)11 = 11.0 (double)(7) /2 = 7.0/2 = 3.5 (double)(7/2) = 3.0 (int)(7.8+(double)(15)/2) = (int)15.3 =15 Java Programming: From Problem Analysis to Program Design, Second Edition

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

  6. The classString 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

  7. The classString 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 7

  8. The classString 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

  9. Some Commonly Used String Methods Java Programming: From Problem Analysis to Program Design, Second Edition 9

  10. Some Commonly Used String Methods Java Programming: From Problem Analysis to Program Design, Second Edition 10

  11. Some Commonly Used String Methods Java Programming: From Problem Analysis to Program Design, Second Edition 11

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

  13. Examples on string methods String s1 , s2 , s3 ; s1 = “abcdefeg” ; System.out.println( s1.length() ); // 8 System.out.println(s1.charAt(3)); //d System.out.println(s1.indexOf(‘e’)); //4 System.out.println(s1.indexOf(“cd”)); //2 System.out.println(s1.toUpperCase()); //ABCDEFEG Java Programming: From Problem Analysis to Program Design, Second Edition 13

  14. Examples on string methods System.out.println(s1.substring(1 , 4)); //bcd System.out.println(s1 + “xyz”); // abcdefegxyz System.out.println( s1.replace(‘d’ ,’D’)); // abcDefeg System.out.println(s1.charAt(4) ); // e System.out.println(s1.indexOf(‘b’)); // 1 System.out.println(s1.indexOf(‘e’,5)); // 6 Java Programming: From Problem Analysis to Program Design, Second Edition 14

  15. Input Reading a Single Character if ch is a charvariable. To input A into ch, you can use the following statement: ch = console.next().charAt(0); 15 Java Programming: From Problem Analysis to Program Design, Second Edition

  16. Parsing Numeric Strings • Integer, Float, and Double are classes designed to convert a numeric string into a number. • These classes are called wrapper classes. • parseInt is a method of the classInteger, which converts a numeric integer string into a value of the type int. • parseFloat is a method of the classFloat and is used to convert a numeric decimal string into an equivalent value of the type float. • parseDouble is a method of the classDouble, which is used to convert a numeric decimal string into an equivalent value of the type double. Java Programming: From Problem Analysis to Program Design, Second Edition 16

  17. Parsing Numeric Strings • A string consisting of only integers or decimal numbers is called a numeric string. • To convert a string consisting of an integer to a value of the type int, we use the following expression: • Integer.parseInt(strExpression) • Example: • Integer.parseInt("6723") = 6723 • Integer.parseInt("-823") = -823 Java Programming: From Problem Analysis to Program Design, Second Edition 17

  18. Parsing Numeric Strings • To convert a string consisting of a decimal number to a value of the type float, we use the following expression: • Float.parseFloat(strExpression) • Example: • Float.parseFloat("34.56") = 34.56 • Float.parseFloat("-542.97") = -542.97 • To convert a string consisting of a decimal number to a value of the type double, we use the following expression: • Double.parseDouble(strExpression) • Example: • Double.parseDouble("345.78") = 345.78 • Double.parseDouble("-782.873") = -782.873 Java Programming: From Problem Analysis to Program Design, Second Edition 18

  19. Formatting Output with printf The syntax to use the method printf to produce output on the standard output device is: System.out.printf(formatString); or System.out.printf(formatString,argumentList); formatString is a string specifying the format of the output and argumentList is a list of arguments. argumentList is a list of arguments that consists of constant values, variables, or expressions. If there is more than one argument in argumentList, the arguments are separated with commas. Java Programming: From Problem Analysis to Program Design, Second Edition 19

  20. Formatting Output with printf System.out.printf("Hello there!"); Consists of only the format string and the statement: System.out.printf("There are %.2f inches in %d centimeters.%n", centimeters / 2.54, centimeters); Consists of both the format string and argumentList. %.2f and %d are called format specifiers. By default, there is a one-to-one correspondence between format specifiers and the arguments in argumentList. The first format specifier, %.2f, is matched with the first argument, which is the expression centimeters / 2.54. Java Programming: From Problem Analysis to Program Design, Second Edition 20

  21. Formatting Output with printf The second format specifier, %d, is matched with the second argument, which is centimeters. The format specifier %n positions the insertion point at the beginning of the next line. If centimeters = 150  150/2.54 =59.05511811023 The o/p would be : There are 59.06 inches in 150 centimeters The output of a printf statement is right-justified by default. To force the output to be left-justified, negative column widths may be used. Java Programming: From Problem Analysis to Program Design, Second Edition 21

  22. Example1 public class Example3_6 { public static void main (String[] args) { int num = 763; double x = 658.75; String str = "Java Program."; System.out.println("123456789012345678901234567890"); System.out.printf ( "%5d%7.2f%15s%n", num, x, str); System.out.printf ("%15s%6d%9.2f %n", str, num, x); } } Java Programming: From Problem Analysis to Program Design, Second Edition 22

  23. Example1 Sample run : 123456789012345678901234567890 763 658.75 Java Program. Java Program. 763 658.75 Java Programming: From Problem Analysis to Program Design, Second Edition 23

  24. Example2 public class Example3_7 { public static void main (String[] args) { int num = 763; double x = 658.75; String str = "Java Program."; System.out.println("123456789012345678901234567890"); System.out.printf("%-5d%-7.2f%-15s ***%n", num, x, str); System.out.printf("%-15s%-6d%- 9.2f ***%n", str, num, x); } } Java Programming: From Problem Analysis to Program Design, Second Edition 24

  25. Example2 Sample Run : 123456789012345678901234567890763 658.75 Java Program. ***Java Program. 763 658.75 *** Java Programming: From Problem Analysis to Program Design, Second Edition 25

  26. Formatting Output with printf Java Programming: From Problem Analysis to Program Design, Second Edition 26

  27. Commonly Used Escape Sequences 27 Java Programming: From Problem Analysis to Program Design, Second Edition

More Related