String is a collection of alphanumeric & special characters and escape sequences enclosed in (Double quotes).

Transcription

1 Strings notes kp Page 1 of 6 Strings - kp String is a collection of alphanumeric & special characters and escape sequences enclosed in (Double quotes). E.g. Bill Gates 1, Rajpur road 25/12/ How\nare\nyou The Data type used for it is String. String is not a primitive data type, it s a class. The advantage of it being a class is that we get a number of string functions to manipulate strings. Example program to store and display a string. { public static void main(string args[]) { String s="java"; System.out.println( s ); Java To input a string we use br.readline() Example program to input and display a string System.out.println( "You entered = "+ s ); Output COMPUTERS You entered = COMPUTERS

2 Strings notes kp Page 2 of 6 String concatenation: The + operator if put between strings or a string and a character, concatenates (joins) the two values. E.g. 1 String a= Sun ; String b= Java ; String c=a+b; Sop(c); SunJava E.g. 2 String s= Computer ; s=s+ s ; Sop(s); Computers Example program: Input the first and the last name of a person in two different variables. Join these to form a complete name. String first,last, name; System.out.println( "Enter first name " ); first=br.readline(); System.out.println( "Enter last name " ); last=br.readline(); name=first+" "+last; //a space will appear between the two. System.out.print( "Full name = "+ name); Enter first name BILL Enter last name GATES Full name = BILL GATES

3 Strings notes kp Page 3 of 6 String functions String functions are functions which operate on strings. We must precede the string function by the string variable name and the dot operator. E.g. s.length() In the function above, the s is the string variable name and length is the function name. String function: length() this function returns the number of characters, including spaces, contained in a string. String s= Java ; Sop( s.length() ); 4 A string is automatically indexed. This means that the first character of the string is assigned a number 0, the second 1 and so on. E.g. String s= Mouse ; The index of M is 0, o is 1, u is 2, s is 3 and e is 4. The index of the first character is always 0 and the last character one less than the length of the string. String function: charat(index) this function returns the character specified in the argument. String s= Java ; Sop( s.charat( 1 ) ); Sop( s.charat( 2 ) ); a v An example program to display the first and the last character of an input string.

4 Strings notes kp Page 4 of 6 System.out.println( "First character = "+s.charat(0) ); System.out.println( "Last character = "+s.charat(s.length()-1) ); MOUSE First character = M Last character = E Program to display each character of a string in a different line for(int i=0; i<s.length(); i++)//this loop generates all the indexes { System.out.println( s.charat(i) ); MOUSE M O U S E Note: Use a for loop as shown above, if you have to process all the characters of a string one by one Programs 1. Write a program to input a string and count the number of the times the letter A appears in it in either case. Hint: use a counter count++ if the character is A or a. 2. Write a program to input a string and display it in reverse. Hint: Reverse the for loop

5 Strings notes kp Page 5 of Write a program to input a sentence string and display the first letter of each word present in it. Each word is separated by a space. (Hint: Print the character which falls after a space) 4. Predict the output of the following program { public static void main(string args[]) { String word="mouse"; String str=""; //A string should be initialised with ""(null) for(int i=0; i<word.length(); i++) { char c=word.charat(i); str=str+c; System.out.println( str ); Solutions: Program 1 int count=0; for(int i=0; i<s.length(); i++) { char c=s.charat(i); if(c=='a' c=='a') { count++; System.out.println( "Frequency of A/a = "+count ); Andhra Bank Frequency of A/a = 3 Program 2

6 Strings notes kp Page 6 of 6 int count=0; for(int i=s.length()-1; i>=0; i--) { char c=s.charat(i); System.out.print( c ); COMPUTERS SRETUPMOC Program 3 System.out.println( "Enter a sentence " ); int count=0; System.out.print( s.charat(0)+" ");//display the first character of the first word for(int i=0; i<s.length(); i++) { char c=s.charat(i); if(c==' ') { System.out.print( s.charat(i+1)+" " );//the index of the character next to i will be i+1 Enter a sentence ALL IS WELL THAT ENDS WELL A I W T E W Answer 4: M MO MOU MOUS MOUSE END