Question: Chapter 8: 2 Dimensional Arrays 1. Hand-write code to declare a two dimensional array of 3 columns and 4 rows. The Array will hold doubles.
Chapter 8: 2 Dimensional Arrays
1. Hand-write code to declare a two dimensional array of 3 columns and 4 rows. The Array will hold doubles. What is the array initialized to by default?
2. Define the following arrays using an initializer list:
a.
1 2 3
2 3 4
5 6 7
b.
1 2
4 5 6
3. Write code to print the arrays below
4. Given the two dimensional array below:
public class Class1 {
public static void main (String [] args) {
int[][] list = { {9, 8}, {6, 5}, {3, 2}, {7, 7} };
a. What is the value of list.length _______________
b. What is the value of list[0].length _______________
You will be asked to write and/or interpret these common array algorithms
1) Finding the highest value in a 2 dim array
2) Finding the lowest value in a 2 dim array
3) Adding the elements of a 2 dim array
4) Adding the elements of a column of a 2 dim array
5) Adding the elements of a row of a 2 dim array
They are all found in the class notes and labs completed in class.
How does the loop change the array?
int [][] matrix = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} };
for (int row=0; row < matrix.length; row++) {
for (int col = 0; col< matrix[0].length; col++) {
if (row == col) matrix[row][col] = matrix[row][col] * 10;
}
}
Chapter 9: Defining Classes and Objects:
1) Constructors: Same name as the class, no return type, run when the object is created
2) Constructors may be overloaded
3) Accessors: return the value of the instance variables
4) Mutators; Change the value of the instance variables
5) Instance variables (or data fields): belong to the object. Private to enforce encapsulation. Can be used in every method of the class
6) Encapsulation: Variables private, getters and setters
7) Static variables: Shared by all objects of the class. One copy
8) Array of Objects: Employee [] theEmployees = new Employee [10];
9) Scope of variables: Where it can be used: block in which it was defined. Local and parameter variables=> method, instance variable=> entire class
10)this the current object needed if the name of parameter variable is the same as the instance variable
UML Diagrams:
Course
-courseName: String
-students: Student []
-numberOfStudents: int
+Course(courseName : String)
+getCourseName() : String
+addStudent (student : Student) : void
+addStudent (studentName: String): void
+dropStudent(studentId: int ) : void
+getStudents() : Student []
+getNumberOfStudents() : int
a. How many constructors does Course have?
b. How many methods that are void?
c. How many methods that return a value?
d. What is the parameter to the method dropStudent?
Write the Widget class.
a. A widget has a name and price.
b. The default for name should be widget
c. Write a constructor (not the no-args), all getters and setters.
d. Add a toString method.
e. Create an object of type Widget.
Consider the Person class below:
public class Person {
private String name;
private int age; public
Person ()
{
}
public void setAge(int age)
{
this.age = age;
}
public void setName(String name)
{
name = name;
}
public int getAge()
{
return age;
}
public String getName()
{
return name;
}
}
Create an object of type Person with name, John, and age 25.
Create a one dimensional Array of Person objects, people, which can hold 100 Person objects:
Write the sumAge method. It calculates the total age of all the Person objects in the people array.
public static int sumAge(Person [] people) {
}
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