Chapter 5 and 7 Test Review
In the following code, what is the printout for list1? class Test { public static void main(String[] args) { int[] list1 = {1, 2, 3}; int[] list2 = {1, 2, 3}; list2 = list1; list1[0] = 0; list1[1] = 1; list2[2] = 2; for (int i = 0; i < list1.length; i++) System.out.print(list1[i] + " "); } }
0 1 2
What is the output of the following code? double[] myList = {1, 5, 5, 5, 5, 1}; double max = myList[0]; int indexOfMax = 0; for (int i = 1; i < myList.length; i++) { if (myList[i] > max) { max = myList[i]; indexOfMax = i; } } System.out.println(indexOfMax);
1
The array index is not limited to int type.
False
The element in the array must be of a primitive data type.
False
The name length is a method in an array
False
You can always convert a for loop to a while loop.
True
_______ declares an array of char.
char[] chars && char chars[]
The JVM stores the array in an area of memory, called _______, which is used for dynamic memory allocation where blocks of memory are allocated and freed in an arbitrary order.
heap
If you declare an array double[] list = {3.4, 2.0, 3.5, 5.5}, list[1] is ________.
2.0
If you declare an array double[] list = {3.4, 2.0, 3.5, 5.5}, the highest index in array list is __________.
3
How many elements are in array double[] list = new double[5]?
5
What is sum after the following loop terminates? int sum = 0; int item = 0; do { item++; sum += item; if (sum > 4) break; } while (item < 5);
6
Analyze the following code. int x = 1; while (0 < x) && (x < 100) System.out.println(x++);
The code does not compile because (0 < x) && (x < 100) is not enclosed in a pair of parentheses.
Which of the loop statements always have their body executed at least once.
The do-while loop
What's the output of the program? public class Test { public static void main(String[] args) { int[] x = {1, 2, 3, 4}; int[] y = x; x = new int[2]; for (int i = 0; i < y.length; i++) System.out.print(y[i] + " "); } }
The program displays 1 2 3 4
What's the output of the program? public class Test { public static void main(String[] args) { int[] oldList = {1, 2, 3, 4, 5}; reverse(oldList); for (int i = 0; i < oldList.length; i++) System.out.print(oldList[i] + " "); } public static void reverse(int[] list) { int[] newList = new int[list.length]; for (int i = 0; i < list.length; i++) newList[i] = list[list.length - 1 - i]; list = newList; } }
The program displays 1 2 3 4 5.
(for-each loop) Analyze the following code: public class Test { public static void main(String[] args) { double[] x = {2.5, 3, 4}; for (double value: x) System.out.print(value + " "); } }
The program displays 2.5 3.0 4.0
Analyze the following code: public class Test { public static void main(String[] args) { int[] a = new int[4]; a[1] = 1; a = new int[2]; System.out.println("a[1] is " + a[1]); } }
The program displays a[1] is 0.
Analyze the following code: public class Test1 { public static void main(String[] args) { xMethod(new double[]{3, 3}); xMethod(new double[5]); xMethod(new double[3]{1, 2, 3}); } public static void xMethod(double[] a) { System.out.println(a.length); } }
The program has a compile error because xMethod(new double[3]{1, 2, 3}) is incorrect.
Analyze the following code: public class Test { public static void main(String[] args) { int[] x = new int[5]; int i; for (i = 0; i < x.length; i++) x[i] = i; //Hint: What is i's value after the loop? System.out.println(x[i]); } }
The program has a runtime error because the last statement in the main method causes ArrayIndexOutOfBoundsException.
Analyze the following code. public class Test { public static void main(String[] args) { int[] x = new int[3]; System.out.println("x[0] is " + x[0]); } }
The program runs fine and displays x[0] is 0.
The while loop and the do loop are equivalent in their expressive power; in other words, you can rewrite a while loop using a do loop, and vice versa.
True
You can always convert a while loop to a for loop.
True
What is i after the following for loop? int y = 0; for (int i = 0; i < 10; i++) { y += i; }
Undefined
Will the following program terminate? int balance = 10; while (true) { if (balance < 9) break; balance = balance - 9; }
Yes
What is the representation of the third element in an array called a?
a[2]
When you pass an array to a method, the method receives __________.
the reference of the array
When you return an array from a method, the method returns __________.
the reference of the array
Assume the signature of the method xMethod is as follows. public static void xMethod(double[] a) Which of the following could be used to invoke xMethod?
xMethod(new double[2]);
What is the output of the following code? int[] myList = {1, 2, 3, 4, 5, 6}; for (int i = myList.length - 2; i >= 0; i--) { myList[i + 1] = myList[i]; } for (int e: myList) System.out.print(e + " ");
1 1 2 3 4 5
The following loop displays _______________. for (int i = 1; i <= 10; i++) { System.out.print(i + " "); i++; }
1 3 5 7 9
How many times will the following code print "Welcome to Java"? int count = 0; while (count < 10) { System.out.println("Welcome to Java"); count++; }
10
Assume int[] t = {1, 2, 3, 4}. What is t.length?
5
How can you initialize an array of two characters to 'a' and 'b'?
char[] charArray = {'a', 'b'}; && char[] charArray = new char[]{'a', 'b'};
What is the number of iterations in the following loop: for (int i = 1; i < n; i++) { // iteration }
n - 1
What is output of the following code? public class Test { public static void main(String[] args) { int list[] = {1, 2, 3, 4, 5, 6}; for (int i = 1; i < list.length; i++) list[i] = list[i - 1]; for (int i = 0; i < list.length; i++) System.out.print(list[i] + " "); } }
1 1 1 1 1 1
Which of the following loops correctly computes 1/2 + 2/3 + 3/4 + ... + 99/100? A: double sum = 0; for (int i = 1; i <= 99; i++) { sum = i / (i + 1); } System.out.println("Sum is " + sum); B: double sum = 0; for (int i = 1; i < 99; i++) { sum += i / (i + 1); } System.out.println("Sum is " + sum); C: double sum = 0; for (int i = 1; i <= 99; i++) { sum += 1.0 * i / (i + 1); } System.out.println("Sum is " + sum); D: double sum = 0; for (int i = 1; i <= 99; i++) { sum += i / (i + 1.0); } System.out.println("Sum is " + sum); E: double sum = 0; for (int i = 1; i < 99; i++) { sum += i / (i + 1.0); } System.out.println("Sum is " + sum);
CD
What is the value in count after the following loop is executed? int count = 0; do { count++; System.out.println("Welcome to Java"); } while (count < 10); System.out.println(count);
10
Analyze the following code. int[] list = new int[5]; list = new int[6];
The code can compile and run fine. The second line assigns a new array to list.
In the following code, what is the printout for list2? class Test { public static void main(String[] args) { int[] list1 = {1, 2, 3}; int[] list2 = {1, 2, 3}; list2 = list1; list1[0] = 0; list1[1] = 1; list2[2] = 2; for (int i = 0; i < list2.length; i++) System.out.print(list2[i] + " "); } }
0 1 2
How many times will the following code print "Welcome to Java"? int count = 0; do { System.out.println("Welcome to Java"); count++; } while (count < 10);
10
How many times will the following code print "Welcome to Java"? int count = 0; while (count < 10) { count++; System.out.println("Welcome to Java"); }
10
What is the output for y? int y = 0; for (int i = 0; i < 5; i++) { y += i; } System.out.println(y);
10
Which of the following loops prints "Welcome to Java" 10 times? A: for (int count = 1; count <= 10; count++) { System.out.println("Welcome to Java"); } B: for (int count = 0; count < 10; count++) { System.out.println("Welcome to Java"); } C: for (int count = 1; count < 10; count++) { System.out.println("Welcome to Java"); } D: for (int count = 0; count <= 10; count++) { System.out.println("Welcome to Java"); }
AB
Show the output of the following code: public class Test { public static void main(String[] args) { int[] x = {1, 2, 3, 4, 5}; increase(x); int[] y = {1, 2, 3, 4, 5}; increase(y[0]); System.out.println(x[0] + " " + y[0]); } public static void increase(int[] x) { for (int i = 0; i < x.length; i++) x[i]++; } public static void increase(int y) { y++; } }
2 1
Analyze the following code: public class Test { public static void main (String args[]) { int i = 0; for (i = 0; i < 10; i++); System.out.println(i + 4); } }
The program compiles despite the semicolon (;) on the for loop line, and displays 14. && The for loop in this program is same as for (i = 0; i < 10; i++) { }; System.out.println(i + 4);
Analyze the following code. int count = 0; while (count < 100) { // Point A System.out.println("Welcome to Java!"); count++; // Point B } // Point C
count < 100 is always true at Point A && count < 100 is always false at Point C
The __________ method sorts the array scores of the double[] type.
java.util.Arrays.sort(scores)
What is the number of iterations in the following loop: for (int i = 1; i <= n; i++) { // iteration }
n
What is the printout after the following loop terminates? int number = 25; int i; boolean isPrime = true; for (i = 2; i < number; i++) { if (number % i == 0) { isPrime = false; break; } } System.out.println("i is " + i + " isPrime is " + isPrime);
i is 5 isPrime is false
What is the printout after the following loop terminates? int number = 25; int i; boolean isPrime = true; for (i = 2; i < number && isPrime; i++) { if (number % i == 0) { isPrime = false; } } System.out.println("i is " + i + " isPrime is " + isPrime);
i is 6 isPrime is false
What would be the result of attempting to compile and run the following code? public class Test { public static void main(String[] args) { double[] x = new double[]{1, 2, 3}; System.out.println("Value is " + x[1]); } }
The program compiles and runs fine and the output "Value is 2.0" is printed.
Analze the following code: import java.util.Scanner; public class Test { public static void main(String[] args) { int sum = 0; for (int i = 0; i < 100000; i++) { Scanner input = new Scanner(System.in); sum += input.nextInt(); } } }
The program compiles and runs, but it is not efficient and unnecessary to execute the Scanner input = new Scanner(System.in); statement inside the loop. You should move the statement before the loop.
What's the output of the program? public class Test { public static void main(String[] args) { int[] x = {1, 2, 3, 4}; int[] y = x; x = new int[2]; for (int i = 0; i < x.length; i++) System.out.print(x[i] + " "); } }
The program displays 0 0
