Download Practice Final Exam Solution

Practice Exam
1. printf
What is the output of the following program? Use the table below to show the appropriate
spacing. The first line of output is already given, as are the first two characters of each
subsequent line; you should show the rest of the output for the other 6 lines (A thru F).
public class Test1Problem5 {
public static void main(String[] args) {
System.out.printf(" 1234567890\n");
System.out.printf("A.%8d\n", 125);
System.out.printf("B.%-10d\n", 125);
System.out.printf("C.%4d%d\n", 125, 277);
System.out.printf("D.%6.2f%4d\n", 1.256, 277);
System.out.printf("E.%7.0f\n", 5.76);
System.out.printf("F.%1d %2d %3d\n", 1, 2, 3);
}
}
1
CSS 161
A
.
B
.
C
.
D
.
E
.
F
.
1
2
3
4
5
6
7
8
1
2
5
7
2
5
1
2
5
2
7
1
.
2
6
2
9
0
7
7
6
1
2
3
Page 1
2. Classes
Define a class, TestList, with the following members:
 Two instance variable:
1) an array of integers to hold the test scores,
2) an integer variable used to indicate the current number of tests.
 A constructor that initializes the array elements to 0 and the integer variable to 0.
public TestList()
 A void method that accepts a single int and adds this to the list.
public void add(int newScore)
 A “toString()” method that returns a single string containing every test score in the list
public String toString()
 A boolean method that return whether the provided test score passed as a parameter is
in the list.
public boolean contains(int testScore)
 A method called “sum” that adds up and returns the sum of all of the numbers currently
in the list
public int sum()
Note that all methods in this class should only calculate and return values, they should not print
anything. The TestList can never grow beyond 10 scores. No comments required.
Write a Driver class, TestListDriver, that creates a TestList object and adds 100, 90, and 72 to
the list. Then print out the TestList array. The output should be:
Scores: 100 90 72
Sum: 262
public class TestList {
private int [ ] testScores= new int[10];
private int count;
public TestList() {
for (int i = 0; i < 10; i++)
testScores[i] = 0;
count = 0;
}
CSS 161
Page 2
public void add(int score ) {
testScores[count] = score;
count++;
}
public String toString( ) {
String strOfScores = "" ;
for ( int i = 0; i < count; i++ )
strOfScores = strOfScores + " " + testScores[i];
return strOfScores;
}
public boolean contains( int testScore) {
for ( int i = 0; i < count; i++ )
if ( testScore == testScores[i] )
return true;
return false;
}
public int sum() {
int sum = 0;
for ( int i = 0; i < count; i++ )
sum += testScores[i];
return sum;
}
}
public class TestListDriver {
public static void main (String [] args) {
TestList tList = new TestList( );
tList.add(100);
tList.add(90);
tList.add(72);
System.out.println("Scores: " + tList);
System.out.println("Sum: " + tList.sum() );
}
}
CSS 161
Page 3
3. String methods
What is the output of the following program? [There are no syntax errors.]
public class FinalExamStringTest {
public static void main(String[] args) {
String s = "March madness";
System.out.printf("a. %d\n", s.length());
System.out.printf("b. %s\n", s.charAt(1));
System.out.printf("c. %d\n", s.indexOf("m"));
System.out.printf("d. %d\n", s.lastIndexOf("a"));
System.out.printf("e. %d\n", s.indexOf("A"));
}
}
a. 13
b. a
c. 6
d. 7
e. -1
4. for loops/if statements
What is the output of the following program? [There are no syntax errors.]
public class FinalExamIfTest1 {
public static void main(String[] args) {
for (int i = 0; i < 5; i++) {
System.out.print(i);
if (i % 2 == 0)
System.out.print(" A");
if (i >= 2)
System.out.print(" B");
System.out.println();
}
}
}
0
1
2
3
4
A
A B
B
A B
CSS 161
Page 4
5. For loops
What is the output of the following program? [There are no syntax errors.]
public class FinalExamForTest {
public static void main(String[] args) {
for (int i = 0; i < 4; i++) {
for (int j = 5; j > i ; j--)
System.out.print(" ");
System.out.print("*");
for (int j = 0; j < i; j++)
System.out.print(" ");
System.out.println("*");
}
}
}
1
2
3
4
5
6
7
*
*
*
*
*
8
9 10
*
*
*
6. Arrays
Code a method called addArray( ) that takes two parameters: the first for an array of base
type int, and the second for an int. The method adds to each array element the second
parameter if the value of the element is even and subtracts the second parameter if the
value of the element is odd; stores each result in another array of base type int; and
returns this new array. Make it a static method.
public static int [ ] addArray(int [ ] array, int number) {
int [ ] newArray = new int[length.array];
for ( int i = 0; i < array.length; i++)
if (array[i] % 2 == 0)
newArray[i] = array[i] + number;
else
newArray[i] = array[i] - number;
return newArray;
}
CSS 161
Page 5
7. Arrays
Write a static method, oddEvenCount( int[ ] array), that takes as a parameter an integer
array and returns a new array (2 elements) that contains the number of even and odd
values in the array. You may assume that the array has at least one element. Count zero as
an even number.
See the following table for example input parameter and return counts.
array
evenOddCount(array
{7, 4, 35, 2, 5, 4, 2, 3}
[4, 4]
{25, -1, 1, 2, -1, 3, 4, 1, -1}
[2, 7]
{100, 2, 56, 0, 2}
[5, 0]
public static int [] oddEvenCount(int [] array) {
int oddCount = 0;
int evenCount = 0;
int [ ] newArray = new int[2];
for ( int i = 0; i < array.length; i++)
if (array[i] % 2 == 0)
evenCount++;
else
oddCount++;
newArray[0] = evenCount;
newArray[1] = oddCount;
return newArray;
}
CSS 161
Page 6
8. File IO/Arrays
Write a method that opens a file containing quiz scores and write out each unique quiz
score to an output file. Open the input file (“scores.txt”) and output file (“nodups.txt”) then
read each integer score from the file, printing out a list (without duplicates) to the
nodups.txt. Assume there can be no more than 10 unique scores.
import java.util.Scanner;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
public class FileIOArrays {
public static void main(String[]args) {
Scanner scoresFile = null;
PrintWriter noDups = null;
int[] scoresWritten = new int[10];
try {
scoresFile = new Scanner(new FileInputStream("scores.txt"));
}
catch (FileNotFoundException e){
System.out.println("Scores file not found");
System.exit(0);
}
try {
noDups = new PrintWriter(new FileOutputStream("nodups.txt"));
}
catch (FileNotFoundException e){
System.out.println("Scores file not found");
System.exit(0);
}
int numwritten = 0;
while(scoresFile.hasNext()) {
int score = scoresFile.nextInt();
boolean written = false;
for(int i = 0; i < scoresWritten.length; i++){
if (score == scoresWritten[i]){
written = true;
}
}
CSS 161
Page 7
if(!written) {
noDups.println(score);
scoresWritten[numwritten] = score;
numwritten++;
}
}
noDups.close();
}
}
9. 2-D Arrays
Write a method that is passed a two-dimensional int array (5 X 5) that counts the total
number of occurrences of 2 or more consecutive integers in a given row. It returns the
value as an int.
See the following table for example input parameter and return count.
Row 1: {5, 4, 4, 2, 1}
Count: 1
Row 2: {6, 6, 7, 7, 7}
Count: 2
Row 3: {3, 3, 2, 3, 3}
Count: 2
Row 4: {3, 1, 2, 1, 3}
Count: 0
Row 5: {3, 3, 3, 3, 3}
Count: 1
Returns: 6
public class TwoDArrarys {
public static void main(String[]args){
int[][] matrix = {{5,4,4,2,1}, {6,6,7,7,7}, {3,3,2,3,3},
{3,1,2,1,3}, {3,3,3,3,3} };
System.out.println("Number of consecutive number: "
+ countConsecutive(matrix));
}
public static int countConsecutive(int[][] matrix) {
int numsecs = 0;
int last = -1;
boolean numberBetween = true;
CSS 161
Page 8
for(int i = 0; i < matrix.length; i++) {
for(int j = 0; j < matrix[i].length - 1; j++) {
if( matrix[i][j] == matrix[i][j + 1] && numberBetween) {
numsecs++;
last = matrix[i][j + 1];
numberBetween = false;
}
if(matrix[i][j + 1] != last) {
numberBetween = true;
}
}
numberBetween = true;
}
return numsecs;
}
}
CSS 161
Page 9