Unit 5 | 5.1 | 5.2 | 5.4 | 5.41 | 5.5 | 5.6 | 5.7 | 5.8 | 5.9 | HW |
Writing Methods
What is a Method?!
A method is a block of code that belong to a class, very similar to a function.
Methods in Java can take inputs (parameters), perform actions, and return a value (or void if no value is returned).
Methods that are created by the programmer to perform tasks are called user-defined methods, while other methods can be built in (like System.out.println()).
Types of methods:
There are many different types of methods in Java, but here I’ll only highlight the two most common ones and the ones used by College board.
Instance Methods: Methods that belong to an instance of a class Instance methods require an object of the class to be used. They operate on objects of the class.
- Can access instance variables and other instance methods within the class
- Can access static variables and methods
Static Methods: Methods that belong to the class itself trather than any instance of the class. Trhey are used for operations taht do not depend on instance-spefific data.
- Can only directly access other static variables and methods.
Here’s a quick example!
- Example of an instance method: addMinion()
- Adds a minion to the list of a villain
- Parameters: String minon
- Example call: gru.addMinion(“Kevin”)
- Second example of an instance method: Villain()
- Changes instance data
- Parameters: string Name, String evilPlan
- Example of a static method: getVillainCount()
- Returns the total amount of Villain instances
- No parameters
- Example call: System.out.println(“There are “ + Villain.getVillainCount() + “ villains in the world.”);
Popcorn hack:
- Add another static method to the Villain class
- Keep it minion themed and fun!
import java.util.ArrayList;
import java.util.List;
public class Villain {
// Instance variables
public String name;
public String evilPlan;
public List<String> minions;
public static int villainCount = 0;
// Constructor for name, plan, and minions
public Villain(String name, String evilPlan) {
this.name = name;
this.evilPlan = evilPlan;
this.minions = new ArrayList<>();
villainCount++;
}
// Instance method to add a minion. LOOK HERE!!
public void addMinion(String minion) {
minions.add(minion);
System.out.println(minion + " has been added to " + name + "'s army.");
}
// Instance method to describe the villain.
public void describeVillain() {
System.out.println(name + " is planning to: " + evilPlan);
System.out.println("They have " + minions.size() + " minions.");
}
// Static method to get the total count of villains
public static int getVillainCount() {
return villainCount;
}
}
public class Main {
public static void main(String[] args) {
Villain.villainCount = 0;
// Create new villains
Villain gru = new Villain("Gru", "steal the moon!");
Villain vector = new Villain("Vector", "take over the world with magnitude and direction!");
System.out.println("=== Adding Minions ===");
// Create some minions
gru.addMinion("Kevin");
gru.addMinion("Stuart");
gru.addMinion("Bob");
// Create some minions for Vector
vector.addMinion("Henchman 1");
System.out.println();
// Describe the villains and their plans
System.out.println("=== Villain Descriptions ===");
gru.describeVillain();
System.out.println();
vector.describeVillain();
System.out.println();
// Get the total count of villains
System.out.println("=== Total Villain Count ===");
System.out.println("There are " + Villain.getVillainCount() + " villains in the world.");
}
}
Main.main(null);
=== Adding Minions ===
Kevin has been added to Gru's army.
Stuart has been added to Gru's army.
Bob has been added to Gru's army.
Henchman 1 has been added to Vector's army.
=== Villain Descriptions ===
Gru is planning to: steal the moon!
They have 3 minions.
Vector is planning to: take over the world with magnitude and direction!
They have 1 minions.
=== Total Villain Count ===
There are 2 villains in the world.
Popcorn hack:
Dr. Nefario is busy assigning work for the minions, and he needs your help to organize his group. Your mission is to write and implement a Java classes for each minion which includes their name, gadgets, personality, and more. Get ready to make Dr. Nefario’s life easier and keep the minions organized!