(Assume all variable are properly declared and all programs are complete).
(You are not allowed to use computer to run the programs.)
1. Circle the correct answers?
a). __________ enable programmers to specify, with a single method declaration, a set of related methods.
a. Overloaded methods.
b. Overriden methods.
c. Generic methods.
b). All generic method declarations have a type parameter section delimited by __________.
a. curly brackets ({ and }).
b. angle brackets (< and >).
c. square brackets ([ and ] ).
c). A recursive method _______________________.
a. is a method containing a loop.
b. calls itself.
c. is part of the java.recursion package.
d). When formulating a recursive solution, what should you consider?
a. base cases and general case
b. base cases only
c. general case only
2. What does the following statements display?
public class MysteryClass
{
public static int mystery( int[] array2, int size )
{
if ( size == 1 )
return array2[ 0 ];
else
return array2[ size - 1 ] + mystery( array2, size - 1 );
} // end method mystery
public static void main( String[] args )
{
int[] array = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int result = mystery( array, array.length );
System.out.printf( "Result is: %d\n", result );
} // end method main
} // end class MysteryClass
//answer for #2
M(a,10) = a[9] + M (a,9) 45+10 = 55
M(a,9) = a[8] + M (a,8)36+9 45
M(a,8) = a[7] + M (a,7)28+8
M(a,7) = a[6] + M (a,6) 21+7
M(a,6) = a[4] + M (a,4)15+6
M(a,5) = a[4] + M (a,4)10+5
M(a,4) = a[3] + M (a,3)6+4
M(a,3) = a[2] + M (a,2) 3+3
M(a,2) = a[1] + M (a,1) 2+1
M(a,1) = a[0] + M (a,0)
Result is : 55
3. Show the output of the following program:
public class RangeSum
{
public static void main(String[] args)
{
int[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9};
System.out.print("The sum of elements 2 through " +
"5 is "+ rangeSum(numbers, 2, 5));
}
public static int rangeSum(int[] array, int start, int end)
{
if (start > end)
return 0;
else
return array[start] + rangeSum(array, start + 1, end);
}
}
//answer for #3
Rangesum (2,5) = array[start] + rangesum (a, start +1, end)
Rs(2,5) array[2] + rs (a, 2+1, 5)
Rs(2,5) 3+ rs (3,5) 15+3 = 18
Rs(3,5) 4 + rs(4,5) 11+4
Rs(4,5) 5 + rs(5,5) 6+5
Rs(5,5) 6 + rs(6,5)
The sum of elements 2 through 5 is 18
4. Show the output of following program:
// MaximumTest.java
// Generic method maximum returns the largest of three objects.
public class MaximumTest
{
public static void main( String[] args )
{
System.out.printf( "Maximum of %d, %d and %d is %d\n\n", 3, 4, 5,
maximum( 3, 4, 5 ) );
System.out.printf( "Maximum of %.1f, %.1f and %.1f is %.1f\n\n",
6.6, 8.8, 7.7, maximum( 6.6, 8.8, 7.7 ) );
System.out.printf( "Maximum of %s, %s and %s is %s\n", "pear",
"apple", "orange", maximum( "pear", "apple", "orange" ) );
} // end main
// determines the largest of three Comparable objects
public static < T extends Comparable< T > > T maximum( T x, T y, T z )
{
T max = x; // assume x is initially the largest
if ( y.compareTo( max ) > 0 )
max = y; // y is the largest so far
if ( z.compareTo( max ) > 0 )
max = z; // z is the largest
return max; // returns the largest object
} // end method maximum
} // end class MaximumTest
//answer #4
Maximum of 3, 4 and 5 is 5
Maximum of 6.6, 8.8 and 7.7 is 8.8
Maximum of pear, apple and orange is pear
5. Show the output of running the class Test in the following code:
import java.util.ArrayList; // Needed for ArrayList class
public class ArrayListDemo3
{
public static void main(String[] args)
{
// Create an ArrayList to hold some names.
ArrayList nameList = new ArrayList();
// Add some names to the ArrayList.
nameList.add("James");
nameList.add("Catherine");
nameList.add("Bill");
// Display the items in nameList and their indices.
for (int index = 0; index < nameList.size(); index++)
{
System.out.println("Index: " + index + " Name: " +
nameList.get(index));
}
// Now remove the item at index 1.
nameList.remove(1);
System.out.println("The item at index 1 is removed. " +
"Here are the items now.");
// Display the items in nameList and their indices.
for (int index = 0; index < nameList.size(); index++)
{
System.out.println("Index: " + index + " Name: " +
nameList.get(index));
}
}
}
//answer #5
Index: 0 Name: James
Index: 1 Name: Catherine
Index: 2 Name: Bill
The item at index 1 is removed. Here are the items now.
Index: 0 Name: James
Index: 1 Name: Bill
6. What is the output of running class C?
import java.util.ArrayList; // Needed for ArrayList class
public class ArrayListDemo1
{
public static void main(String[] args)
{
// Create an ArrayList to hold some names.
ArrayList nameList = new ArrayList();
// Add some names to the ArrayList.
nameList.add("James");
nameList.add("Catherine");
nameList.add("Bill");
// Display the size of the ArrayList.
System.out.println("The ArrayList has " +
nameList.size() +
" objects stored in it.");
// Now display the items in nameList.
for (int index = 0; index < nameList.size(); index++)
System.out.println(nameList.
}
}
// Answer # 6
The ArrayList has 3 objects stored in it.
James
Catherine
Bill
7. What is the output of running the class C.
public class C {
public static void main(String[] args) {
Object[] o = {new A(), new B()};
System.out.print(o[0]);
System.out.print(o[1]);
}
}
class A extends B {
public String toString() {
return "A";
}
}
class B {
public String toString() {
return "B";
}
}
a. AB
b. BA
c. AA
d. BB
e. None of above
8. What is the output of running class C?
class A {
public A() {
System.out.println(
"The default constructor of A is invoked");
}
}
class B extends A {
public B(String s) {
System.out.println(s);
}
}
public class C {
public static void main(String[] args) {
B b = new B("The constructor of B is invoked");
}
}
a. none
b. "The constructor of B is invoked"
c. "The default constructor of A is invoked" "The constructor of B is invoked"
d. "The default constructor of A is invoked"
9. Analyze the following code:
public class Test1 {
public Object max(Object o1, Object o2) {
if ((Comparable)o1.compareTo(o2) >= 0) {
return o1;
}
else {
return o2;
}
}
}
a. The program has a syntax error because Test1 does not have a main method.
b. The program has a syntax error because o1 is an Object instance and it does not have the compareTo method.
c. The program would compile if ((Comparable)o1.compareTo(o2) >= 0)
is replaced by ((ComparableTo(o1).compareTo(
d. b and d are both correct.
10.a). Complete the code:
public class Test {
public static void main(String[] args) {
int i = 4; int j = 5;
// Fill in the code to invoke the sum method and display the sum of i and j.
}
Sysem.out.println(sum(I,j));
}
Public static int sum ( int I, int j )
Return (I,j)
}
}
public static int sum(int i, int j) {
// Fill in the code here to return the sum of i and j.
}
}
b). Complete the code:
public class Test {
public static void main(String[] args) {
int i = 4; int j = 5;
// Fill in the code to invoke the printSum method to display the sum of i and j.
10 b
Public static void main (string [] args){
Int I = 4 j = 5
printSum(i.j)
}
Public static void printSum(int I, int j)
{
System.out.println(i+j)
}
public static void printSum(int i, int j) {
// Fill in the code here to display the sum of i and j.
}
}
10 a
}
Sysem.out.println(sum(I,j));
}
Public static int sum ( int I, int j )
Return (I,j)
}
10 b
Public static void main (string [] args){
Int I = 4 j = 5
printSum(i.j)
}
Public static void printSum(int I, int j)
{
System.out.println(i+j)
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