Instance Method Review - CIS 1068 Program Design and Abstraction

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Instance Method Review - CIS 1068 Program
Design and Abstraction

• Zhen Jiang
• CIS Dept.
• Temple University
• 1050 Wachman Hall, Main Campus
• Email zhen.jiang_at_temple.edu

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Table of Contents

• Introduction
• Declaration and call
• Access and scope

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Introduction

• Why?
• Why loop
• Why array
• Why method
• Why object (the host of instance method)?

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• Every thing under the control inside of object
  (which must be declared in the class, as a
  general template to cover all possible
  changes/statuses)

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Dog class state String name, breed int
age behavior writeOutput ( )
getAgeInHumanYears ( )?

• Dog object
• balto
• state Balto (name)
• 8 (age)
• Siberian Husky (breed)
• behaviorgetAgeInHumanYears ( )
• writeOutput ( )

• Dog object
• scooby
• state Balto (name)
• 8 (age)
• Siberian Husky (breed)
• behaviorgetAgeInHumanYears ( )
• writeOutput ( )

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Declaration and Call

• No more static
• How to use instance method m()?

public class A public void m()

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public class A public void m()
public void m2() m()

• public class B
• public void m()
• public void m3()
• m()
• A a //a.m is not supported
• A b new A ()
• b.m()

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public class A public void m()
public static void m2() A a
new A() a.m()
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• For comparison

public class A public static void m()
public void m2() m()

• public class B
• public void m()
• public void m3()
• m()
• A.m()

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• For comparison

public class A public void m1()
System.out.println("A's m1") m2()public
static void m2()System.out.println("A's static
m2")

• public class B public void m1() A a new
  A() a.m1() A.m2()public static void
  m2() System.out.println("B's static m2") B b2
  new B() b2.m1()public static void
  main(String args) A a new A() B b new
  B() b.m1() B.m2()

A's m1 A's static m2 A's static m2 B's static
m2 A's m1 A's static m2 A's static m2
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• Constructor
• Name
• No return
• Not static
• Related to the use of new
• Overloading

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• Mutator
• Argument and parameter
• Type (compatible overloading)
• Primitive type and reference type (array
  object)
• Accessor
• Return
• toString

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• Constructor

public class A public A()
public A(int x)

• public class B
• public void m3()
• A a new A()
• A b new A(2)

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• Mutator and accessor

public class A public A()
public void a()
public void A()

• public class B
• public void m3()
• A a new A()
• a.a()
• a.A() // but very confused!

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• When an object is printed or concatenated with a
  String, Java calls the object's toString method.
• System.out.println("p1 is " p1)
• is equivalent to
• System.out.println("p1 is " p1.toString())
• Note Every class has a toString method.

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• toString

public class A private int x 2 public
A() public String
toString () // no parameter! return a
x

• public class B
• public void m3()
• A a new A()
• System.out.println(a)

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Access and Scope

• Attribute (property, data field, etc)
• What is this
• Parameter

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• Attribute
• what is this

public class A private int x public
A(int y) x y public void
m(int x) // int x this.x x
public String toString() return x

• public class B
• public void m3()
• A a new A(2)
• a.m(3)
• System.out.println(a)

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• Parameter

public class A public int x public A(int
y) x y public void n()
// another method // other than m
public void m(A a) // x and a.x // n()
and a.n()

• public class B
• public void m3()
• A a new A(2)
• A b new A(3)
• a.m(b)

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• Parameter

public class A private int x public
A(int y) x y public void
n() // another method // other than m
public int getX() return x
public void m(A a) // x and a.getx() //
n() and a.n()

• public class B
• public void m3()
• A a new A(2)
• A b new A(3)
• a.m(b)

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• ArrayOperation.java vs. ArrayOperations.java
• http//www.cis.temple.edu/jiang/ArrayOperation.ja
  va
• http//www.cis.temple.edu/jiang/ArrayOperations.j
  ava