All Flashcards
What are the differences between accessor and mutator methods?
Accessor: Retrieves value of a private variable. Mutator: Modifies value of a private variable.
What are the differences between static and instance variables?
Static: Belongs to the class, shared by all objects. Instance: Belongs to each object, unique to each object.
What are the differences between global and local scope?
Global: Accessible throughout the program. Local: Accessible only within a specific block of code.
What is the definition of a class?
A blueprint for objects, containing variables and methods.
What is an instance variable?
A variable that stores data within a class.
What is a constructor?
A special method to create and initialize objects of a class.
What is an accessor method?
A method (getter) used to retrieve the value of a private variable.
What is a mutator method?
A method (setter) used to modify the value of an instance variable.
What is a static variable?
A variable that works across all objects of a class, accessible without creating an object.
What is a static method?
A method that works across all objects of a class, accessible without creating an object.
What is scope in programming?
The visibility and accessibility of variables, functions, and other elements of a program.
What is global scope?
Visibility and accessibility of an element throughout the entire program.
What is local scope?
Visibility and accessibility of an element within a specific block of code.
What does the 'this' keyword refer to?
The current instance of an object.
What is a comment in Java?
A piece of text that the computer will not recognize as code and will not try to execute.
What does the following code output? public class Test { private int x = 5; public static void main(String[] args) { Test t = new Test(); System.out.println(t.x); } }
5
Identify the error in the following code: public class Example { private int value; public void Example(int v) { value = v; } }
The constructor has a return type. It should be 'public Example(int v)' without 'void'.
What does the following code output? public class Counter { private static int count = 0; public Counter() { count++; } public static int getCount() { return count; } public static void main(String[] args) { Counter c1 = new Counter(); Counter c2 = new Counter(); System.out.println(Counter.getCount()); } }
2
Identify the error in the following code: public class MyClass { private int x; public void setX(int val) { x = value; } }
The variable 'value' is not defined in the setX method. It should be 'x = val;'.
What does the following code output? public class Point { int x, y; public Point(int x, int y) { this.x = x; this.y = y; } public static void main(String[] args) { Point p = new Point(2, 3); System.out.println(p.x + ", " + p.y); } }
2, 3
Identify the error in the following code: public class Circle { private double radius; public double getArea() { return 3.14 * radius; } }
radius is not initialized
What does the following code output? public class Test { public static void main(String[] args) { String str = "Hello"; modifyString(str); System.out.println(str); }
public static void modifyString(String s) {
s = s + " World";
}
}
Hello
Identify the error in the following code: public class Example { public static void main(String[] args) { int num = 5; increment(num); System.out.println(num); } public void increment(int n) { n++; } }
The increment method is not static and is being called from a static method.
What does the following code output? public class MyClass { int x; public MyClass(int x) { this.x = x; } public static void main(String[] args) { MyClass obj1 = new MyClass(10); MyClass obj2 = obj1; obj2.x = 20; System.out.println(obj1.x); } }
20
Identify the error in the following code: public class Rectangle { private int length; private int width;
public Rectangle(int l, int w) { length = l; width = w; }
public int area() { return length * width; }
public static void main(String[] args) { Rectangle rect = new Rectangle(5, 10); System.out.println(rect.Area()); } }
Method name should be area(), not Area().