Question

In this exercise you will debug the code which has been provided in the starter file. The code is intended to take two strings, s1 and s2 followed by a whole number, n, as inputs from the user, then print a string made up of the first n letters of s1 and the last n letters of s2. Your job is to fix the errors in the code so it performs as expected (see the sample run for an example).

Sample run
Enter first string
sausage
Enter second string
races
Enter number of letters from each word
3
sauces
Note: you are not expected to make your code work when n is bigger than the length of either string.
1 import java.util.Scanner;
2
3 public class 02_14_Activity_one {
4 public static void main(String[] args) {
5
6 Scanner scan = Scanner(System.in);
7
8 //Get first string
9 System.out.println("Enter first string");
10 String s1 = nextLine(); 1
11
12 //Get second string
13 System.out.println("Enter second string");
14 String s2 = Scanner.nextLine();
15
16 //Get number of letters to use from each string
17 System.out.println("Enter number of letters from each word");
18 String n = scan.nextLine();
19
20 //Print start of first string and end of second string
21 System.out.println(s1.substring(1,n-1) + s2.substring(s1.length()-n));
22
23
24 }

Answer 1

Here is the corrected program:

import java.util.Scanner; //to accept input from user

public class 02_14_Activity_one { //class name

public static void main(String[] args) { //start of main method

Scanner scan = new Scanner(System.in); //creates Scanner class object

System.out.println("Enter first string"); //prompts user to enter first string

String s1 = scan.nextLine(); //reads input string from user

System.out.println("Enter second string"); //prompts user to enter second string

String s2 = scan.nextLine(); //reads second input string from user

System.out.println("Enter number of letters from each word"); //enter n

int n = scan.nextInt(); //reads value of integer n from user

System.out.println(s1.substring(0,n) + s2.substring(s2.length() - n ));

} } //uses substring method to print a string made up of the first n letters of s1 and the last n letters of s2.

Step-by-step explanation:

The errors were:

1.

Scanner scan = Scanner(System.in);

Here new keyword is missing to create object scan of Scanner class.

Corrected statement:

Scanner scan = new Scanner(System.in);

2.

String s1 = nextLine();

Here object scan is missing to call nextLine() method of class Scanner

Corrected statement:

String s1 = scan.nextLine();

3.

String s2 = Scanner.nextLine();

Here class is used instead of its object scan to access the method nextLine

Corrected statement:

String s2 = scan.nextLine();

4.

String n = scan.nextLine();

Here n is of type String but n is a whole number so it should be of type int. Also the method nextInt will be used to scan and accept an integer value

Corrected statement:

int n = scan.nextInt();

5.

System.out.println(s1.substring(1,n-1) + s2.substring(s1.length()-n));

This statement is also not correct

Corrected statement:

System.out.println(s1.substring(0,n) + s2.substring(s2.length() - n ));

This works as follows:

s1.substring(0,n) uses substring method to return a new string that is a substring of this s1. The substring begins at the 0th index of s1 and extends to the character at index n.

s2.substring(s2.length() - n ) uses substring method to return a new string that is a substring of this s2. The substring then uses length() method to get the length of s2 and subtracts integer n from it and thus returns the last n characters of s2.

The screenshot of program along with its output is attached.