String Handling

A String object cannot be modified after it is created. (T/F)

The length of a String object s1 can be obtained using the expression s1 length. (T/F)

Which of the following methods belong to the String class ?

Given the code

String s1 = "yes" ;
String s2 = "yes" ;
String s3 = new String(s1) ;

Which of the following would equate to False ?

Suppose that s1 and s2 are two strings. Which of the statements or expressions are incorrect ?

Given the code :

String s = new String("abc");

Which of the following calls are invalid ?

Which of these class is superclass of String and StringBuffer class?

Which of these methods of class String is used to obtain length of String object?

Which of these methods of class String is used to extract a single character from a String object?

Which of these constructors is used to create an empty String object?

Which of these is an incorrect statement?

What are String and StringBuffer classes of Java?

How are Strings different from StringBuffers ?

How can you convert a numeric value enclosed in a string format ?

Write the return type of the following library functions :

State the data type and values of a and b after the following segment is executed.

String s1 = "Computer", s2 = "Applications"; 
a = (s1.compareTo(s2));
b = (s1.equals(s2));

What do the following functions return for :

String x = "hello"; 
String y = "world";

(i) System.out.println(x + y);

(ii) System.out.println(x.length( ));

(iii) System.out.println(x.charAt(3));

(iv) System.out.println(x.equals(y));

What will the following code output ?

String s = "malayalam" ;
System.out.println(s.indexOf('m')); 
System.out.println(s.lastIndexOf('m'));

If:

String x = "Computer";  
String y = "Applications";

What do the following functions return?

(i) System.out.println(x.substring(1,5));

(ii) System.out.println(x.indexOf(x.charAt(4)));

(iii) System.out.println(y + x.substring(5));

(iv) System.out.println(x.equals(y));

State the method that:

(i) converts a string to a primitive float data type.

(ii) determines if the specified character is an uppercase character.

What will be the output of the following code snippet when combined with suitable declarations and run?

StringBuffer city = new StringBuffer("Madras"); 
StringBuffer string = new StringBuffer( ); 
string.append(new String(city)); 
string.insert(0, "Central "); 
String.out.println(string);

What will be the output for the following program segment?

String s = new String ("abc");
System.out.println(s.toUpperCase( ));

Give the output of the following program :

class MainString
{
    public static void main(String[ ] args)
    {
        StringBuffer s = new StringBuffer("String"); 
        if((s.length( ) > 5) && 
        (s.append("Buffer").equals("X")))
        ;	// empty statement
        System.out.println(s);
    }
}

Write a program to do the following :

(a) To output the question "Who is the inventor of Java" ?

(b) To accept an answer.

(c) To print out "Good" and then stop, if the answer is correct.

(d) To output the message "try again", if the answer is wrong.

(e) To display the correct answer when the answer is wrong even at the third attempt and stop.

import java.util.Scanner;

public class KboatQuiz
{
    public static void main(String args[])
    {
        Scanner in = new Scanner(System.in);
        
        String q = "Who is the inventor of JAVA?";
        String a = "James Gosling";
        int i;
        
        System.out.println(q);
        
        for(i = 1; i <= 3; i++)
        {
            String ans = in.nextLine();
            ans.trim();
            if(ans.equalsIgnoreCase(a))
            {
                System.out.println("Good");
                break;
            }
            else if(i < 3)
            {
                System.out.println("Try Again");
            }
        }
        
        if(i == 4)
        {
            System.out.println("Correct Answer: " + a);
        }
    }
}

Write a program to extract a portion of a character string and print the extracted string. Assume that m characters are extracted, starting with the nth character.

import java.util.Scanner;

public class KboatExtractSubstring
{
    public static void main(String args[])  
    {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter string : ");
        String s = in.nextLine();
        int len = s.length();
        System.out.print("Enter start index : ");
        int n = in.nextInt();
        
        if(n < 0 || n >= len)
        {
            System.out.println("Invalid index");
            System.exit(1);
        }
        
        System.out.print("Enter no. of characters to extract : ");
        int m = in.nextInt();
        
        int substrlen = n + m;
        if( m <= 0 || substrlen > len)
        {
            System.out.println("Invalid no. of characters");
            System.exit(1);
        }       

        String substr = s.substring(n, substrlen);
        System.out.println("Substring = " + substr); 
    }
}

Write a program, which will get text string and count all occurrences of a particular word.

import java.util.Scanner;

public class KboatWordFrequency
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter a sentence:");
        String str = in.nextLine();
        System.out.println("Enter a word:");
        String ipWord = in.nextLine();
        str += " ";
        String word = "";
        int count = 0;
        int len = str.length();

        for (int i = 0; i < len; i++) {
            if (str.charAt(i) == ' ') {

                if (word.equalsIgnoreCase(ipWord))
                    count++ ;

                word = "";
            }
            else {
                word += str.charAt(i);
            }
        }
        
        if (count > 0) {
            System.out.println(ipWord + " is present " + count + " times.");
        }
        else {
            System.out.println(ipWord + " is not present in sentence.");
        }
        
    }
}

Write a program to accept a string. Convert the string to uppercase. Count and output the number of double letter sequences that exist in the string.

Sample Input : "SHE WAS FEEDING THE LITTLE RABBIT WITH AN APPLE"

Sample Output : 4

import java.util.Scanner;

public class KboatLetterSeq
{
    public static void main(String args[]) {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter string: ");
        String s = in.nextLine();
        String str = s.toUpperCase();
        int count = 0;
        int len = str.length();
        
        for (int i = 0; i < len - 1; i++) {
            if (str.charAt(i) == str.charAt(i + 1))
                count++;
        }
        
        System.out.println("Double Letter Sequence Count = " + count);
        
    }
}

Design a class to overload a function check( ) as follows :

(i) void check(String str, char ch) - to find and print the frequency of a character in a string.
Example:
Input :
str = "success" ch= 's'

Output :
number of s present is = 3

(ii) void check (String s1) - to display only vowels from string s1, after converting it to lower case.
Example:
Input:
sl = "computer"
Output : o u e

public class KboatOverload
{
    void check (String str , char ch ) {
        int count = 0;
        int len = str.length();
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (ch == c) {
                count++;
            }
        }
        System.out.println("Frequency of " + ch + " = " + count);
    }
    
    void check(String s1) {
        String s2 = s1.toLowerCase();
        int len = s2.length();
        System.out.println("Vowels:");
        for (int i = 0; i < len; i++) {
            char ch = s2.charAt(i);
            if (ch == 'a' ||
                ch == 'e' ||
                ch == 'i' ||
                ch == 'o' ||
                ch == 'u')
                System.out.print(ch + " ");
        }
    }
}