Question

1. Given the following code:

public static void foo3(String s)

{

if (s.length() >0)

{

System.out.print(s.charAt(s.length() -1));

foo3(s.substring(0, s.length() -1));

}

}

What is the output of: foo3(“”);

2, You coded the following in the file Test.java :

System.out.println( foo(5));

//more code here

public static int foo(int n) //line 9

{

if (n = = 0)

   return 1;

else

   System.out.println(n* foo(n-1) );

}                                    //line 15

At compile time, you get the following error:

Text.java: 15: missing return statement

}                                 //line 15

^

1 error

Explain what the problem is and how to fix it.

3) Fill in the missing code:

This recursive method returns “even” if the length of a give String is even, and “odd” if the length of the String is odd.

public static String foo(String s)

{

if (s.length() ==0)

   return “even”;

else if (s.length() = = 1)

   return “odd”;

else

    //the code goes here

}

Answer 1

Question 1:
"".length() is 0
As it is not greater than 0 it does not prints anything.

Question 2:
public static int foo(int n) //line 9
{
    if (n == 0)
        return 1;
    else
        // we have to return value without printing it
        return n* foo(n-1);
}

Question 3:
public static String foo(String s)
{
    if (s.length() ==0)
       return "even";
    else if (s.length() == 1)
       return "odd";
    else
        return foo(s.substring(2));
}