/* 
Writer: SP
Date: March 25th
References: knowt & Fiveable
Unit 5: Writing Classes */

Classes

• Class- A blueprint for an object.

• The name of your class should refer to the purpose and function of the class, similar to how you name your variables.

public class Plant {
   // Instance Variables --------
   private String Species;
   private double height;
   // --------------------------
   
   // Constructor
   public Plant(String species, double height) {
      // Implementation not shown
   }
}

• Note: Remember your indentations!! It needs to be correctly indented for the code to be considered a part of the class.

• If we don’t put value, the String variable will return ‘null’

• int will return 0

• double will return 0.0

In classes, variable declarations are foun
d at the top of the code right after the header.

Methods

• Method- A group of code that performs a specific task.

• Accessor Methods:

  • It is a method that allow other clients (objects, classes, and users) to access the data of an object.

  • There are two types of accessor method:

    • Getter methods

      • Returns the specific piece of data.

    class Student
    {
        private String name;
        private String email;
        private int id;
    
        public Student(String initName, String initEmail, int initId)
        {
            name = initName;
            email = initEmail;
            id = initId;
        }
    
        // accessor methods - getters
        /** getName() @return name */
        public String getName()
        {
            return name;
        }
    
        /** getEmail() @return email */
        public String getEmail()
        {
            return email;
        }
    
        /** getName() @return id */
        public int getId()
        {
            return id;
        }
    }

    • toString()

      • Return the information about an object as a string.

    class Student
    {
        private String name;
        private String email;
        private int id;
    
        public Student(String initName, String initEmail, int initId)
        {
            name = initName;
            email = initEmail;
            id = initId;
        }
    
        // toString() method
        public String toString()
        {
            return id + ": " + name + ", " + email;
        }
    }

• Mutator Methods:

  • Also called as setter methods.

    class Student
    {
        // Instance variable name
        private String name;
    
        /**
         * setName sets name to newName
         *
         * @param newName
         */
        public void setName(String newName)
        {
            name = newName;
        }
    
        public static void main(String[] args)
        {
            // To call a set method, use objectName.setVar(newValue)
            Student s = new Student();
            s.setName("Ayanna");
        }
    }

Writing Methods:

• Method headers:

public static void main (String args[])

public String sayHello()

protected static int addNums(int a, int b)

public void printSum(double a, double b, int c, boolean flag, String text)

Static Variables: & Methods

• We don’t need an object to use this variable & method.

• It is belong to class itself, so we can access easily.

• Static methods cannot access or change the values of instance variables.

• Static methods do not have a .this reference

• Static methods can access or change the values of static variables.

• We can understand the static variables and methods are for lazy people.

• If we write easy code, actually we don’t need non-static thing.

  • Example: pi ≈ 3.4.

    • It doesn’t change, it makes a lot of works if we make object.

    • Math.Pi.

class ClassName
{
  // static variable
  public static type variableName;

  // static method
  public static returnType methodName(parameters)
  {
        // implementation not shown
  }
}
// To call a static method or variable, use the Class Name
System.out.println(ClassName.staticVariable);
ClassName.staticMethod();

Scope: There are two types of scope

• Local Scope: a variable can only be used inside a particular method or constructor, not outside.

  • Parameter, local variable

• Global Scope: can be used outisde that method or constructor at least throughout the class.

  • Instance Variable

.this keyword:

• refer to the same instance variable.

public class Assignment {
  private boolean correctAnswer; // represents the answer to an assignment, either T/F

  /** Makes a new assignment with one True/False question and sets the correct answer
  */
  public Assignment(boolean correctAnswer) {
    this.correctAnswer = correctAnswer;
  }

What is an algorithm?

• An algorithm is a step-by-step procedure or set of rules for solving a specific problem or completing a specific task.