Lab session 3 and 4

1. Lab session3 and 4 Topics to be covered Escape sequences Variables /identifiers Constants assignment statement String concatenation String methods

2. ESCAPE SEQUENCES • Java defines several Escape sequences to represent Special characters. • An escape sequence begins with a backslash character (\) and indicates a character or characters that follow should be interpreted in some special way.

3. What does \t do • \t - tab • When u use this in a println statement • System.out.println(“Roses are red,\t Violets are blue,\t,Sugar is sweet”) • OUTPUT Roses are red, Violets are blue , Sugar is sweet

4. Escape Seq Meaning \b backspace \t tab \n newline \r carriage return \” Double quote \’ Single quote \\ backslash

5. What does \n do • \n - newline • When u use this in a println statement • System.out.println(“Roses are red,\n Violets are blue,\n Sugar is sweet”); OUTPUT Roses are red, Violets are blue , Sugar is sweet

6. What does \” do • \n” - Double quote • When u use this in a println statement • System.out.println(“\ Roses are red,\”Violets are blue”,\n Sugar is sweet”); OUTPUT Roses are red, “Violets are blue” , Sugar is sweet

7. What does \’ do • \’ - Single quote • When u use this in a println statement • System.out.println(“Roses are red, \‘Violets are blue\’Sugar is sweet.”); OUTPUT Roses are red, ‘Violets are blue’, Sugar is sweet.

8. What does \\ do • \\ - backslash • When u use this in a println statement • System.out.println(“Roses are red\\Violets are blue\\Sugar is sweet.”); OUTPUT Roses are red\Violets are blue\Sugar is sweet.

9. What does \b do • \’ - backspace • When u use this in a println statement • System.out.println(“Roses are red, \bViolets are blue,\bSugar is sweet.”); OUTPUT Roses are red, Violets are blue,Sugar is sweet.

10. String Concatenation • Strings that are printed using a print statement can be concatenated using + • Eg • System.out.println(“Roses are red”+“ ” +“Violets are blue” ); OUTPUT Roses are red Violets are blue

11. VARIABLES /IDENTIFIERS • A Variable is a name for a location in the memory used to hold a data value num=25 memory num 25

12. Eg public class keys { Public static void main(String args[]) { int key ; //declaration statement key = 88; //initialization statement System.out.println(“A piano has” + key + “keys.”); System.out.println( key ); } OUTPUT: A piano has 88 keys 88

13. Primitive Data type There are 8 data types in java • Integer - has 4 subsets (byte, short, int,long) • Floating point numbers - 2 subsets ( float, double) • Boolean • Character

14. Examples: • int num; // num can store whole numbers • float average; // average can store decimal numbers • char ch; // stores alphabets • Boolean value; //stores either True/False

15. INTIALISATION STATEMENT • num=23; • average=23.00; • ch= ‘s’; • value=true;

16. Assignment statement • Assignment statement –assigns a value to a variable. Public class assign { Public static void main (String args[]) { int no; no=89; int num=56; //assignment st System.out.println(num); System.out.println (“The no is :“+no); }

17. Arithmetic expression • An expression is a combination of one or more operators and operands • the basic arithmetic operations defined for integer type and floating point type are • addition(+),subtraction(-,multiplication(*),division(/). • Java has one more arithmetic operation remainder(%) • 17%4 will return 1 • a= b + c; a,b,c – operands + -- operator

18. Operator precedence • Result=14+8/2; ans=18 ans=11 correct ans is 18 operator precedence hierarchy division/multiplication/% add/sub /concatenation assignment

19. Result=(14+8)/2; ans=11; • result=((18-4)*(2+2)); =(14*4) = 56 expression should be syntactically correct no of left parenthesis should be =no of right parenthesis Result=((19+6)%3)*3); //invalid Result=2+8-6; usually u start from left when same level of precedence

20. objects • Class is used to define an object • Class name is nothing but type of object; • String name; //declaration 1st step • The above declaration creates a reference to string object • No object actually exist • To create an obj use NEW operator: • name=new String (“Adam”); //obj created 2nd step

21. 1st and 2nd can be combined • String name=new String (“Adam”); • The String class has a no of methods Which its objects can use They are charat,replace,substring,length, toLowercase,toUppercase, concat,equals

22. String methods • String(String str) • Constructor: creates a new string object with the same characters As str • Eg String name=new String(“kenny”); Is eqvivalent to String name=“kenny”;

23. Length method • Int length () • Returns the no of characters in the string • Eg String greeting= “Hello!”; greeting. length(); returns 7

24. Lowercase • String toLowerCase() • Returns a new string identical to this string except all uppercase letters converted to lowercase • Eg String greeting= “Hello!”; greeting. toLowerCase(); returns “hello!”.

25. UPPER CASE • String toUpperCase() • Returns a new string identical to this string except all lowercase letters converted to uppercase Eg String greeting= “Hello!”; greeting. toLowerCase(); returns “HELLO!”.

26. Trim • String trim() • Returns a new string identical to this string but with leading and trailing white space removed String pause= “ hhh “; pause. trim() returns “hhh”.

27. concatenation • String concat(String str) • Returns a new string consisting of this string concatenated with str • Eg String name=new String (“kenny”); name.concat(“ is great “) returns “kenny is great”;

28. Char at • Char charat(int index) • Returns a character at specified index • eg String name=new String (“kenny”); name.charat(0) returns ‘k’; name.charat(4) returns ‘y’;

29. Substring • String substring(int start) • Returns a substring of a string starting from index till end of this string. • Eg String name=new String (“kenny”); name.substring(2) returns “nny”;

30. String substring(int start,int end) • Returns a substring of a string starting from index start through but not including index endof this string. • Eg String name=new String (“kenny”); name.substring(2,4) returns “nn”;

31. Replace • String replace(char old,char new) Returns a new string identical to this string except that every occurrence of old is replaced by new. • Eg String name=new String (“kenny”); name. replace (‘n’ ,’l’) returns “kelly”;

32. equals • Boolean equals(String str); • Returns true if the string contains the same characters as str and false otherwise (including case) String greeting= “Hello!”; greeting. equals(“Hello”) returns true. but greeting. equals(“HELL0”) returns false

33. equalsIgnorecase • Boolean equalsIgnoreCase(String str); • Returns true if the string contains the same characters as str and false otherwise (without regard to case); String greeting= “Hello!”; greeting. equals(“HELL0”) returns true