1. Lab session 3 and 4 Topics to be covered Escape sequences Escape sequences Variables /identifiers Variables /identifiers Constants Constants assignment statement assignment statement String concatenation String concatenation String methods 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 25 num memory

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 1 st 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 2 nd step

21. 1 st and 2 nd 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