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JavaSummery	Hadi Asemi		\hypersetup{colorlinks=True, allbordercolors={0 0 0}, pdfborderstyle={/S/U/W 1} } -->	blue	left=1cm,right=1cm,top=2cm,bottom=2cm	\usepackage{fancyhdr} \pagestyle{fancy} \fancyfoot{} \fancyhead{} \fancyfoot[R]{\thepage\ } \renewcommand{\headrulewidth}{2pt} \renewcommand{\footrulewidth}{2pt} \fancyhead[L]{CPE 203} \fancyhead[R]{Hadi Asemi} \fancyhead[C]{Java} \newlength\FHoffset \setlength\FHoffset{1cm}

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Definitions:

• OOP is a programing technique that focuses on the data(=objects) and on the interfaces to that object.

• Object: Is the instance of the class

• Classes: A class is the template or blueprint from which objects are made.

  • Static variable:

    • Belong to the class

    • Accessed by: ClassName.VARIABLE_NAME

• Superclass: class above another in a hierarchy of classses

• Subclass: inherits form parent and is a version of the parent class

• Encapsulation(sometimes called information hiding): is simply combining data and behavior in one package hiding the implementation details from the users of the objects.

• Instance variables: are variables defined in a class, but outside the body of methods. Instance variables are filled when each object is instantiated and belong the object.

• Class Variables: belongs to the class and the value in that variable is shared by every instance of the class by the class itself.

• Constructor: set data's values

• Methods: Manipulate and access data

• Public: is keyword which declares a member's access as public.

• Private: is a Java keyword which declares a member's access as private.

• Static: object belongs specifically to the class, instead of instances of that class.

• Is-a: inheritance/interfaces

• has-a: composition/aggresgation

Three key characteristics of objects:

• The object's behavior

• The object's state

• The object's identity

Array:

int[]array= new int[20]; // allocating memory for array. it will be fixed sized
array[0]=5; //declaring first element array

//for loop - if nums is Array
for (int i = 0; i < nums.length i++){
  //nums[i];
}

//for each loop
for (int i: nums){
  //do stuff with i
}

ArrayList:

ArrayList<String>words=new ArrayList<String>();

ArrayList<Integer>num=new ArrayList<Integer>();

LinkedList<String> ll = new LinkedList<>();  

num.add(1);

num.get(0); // we need put index

//remove element base on index
num.remove(1);


//for loop - if nums is ArrayList
for (int i = 0; i < nums.size(); i++){
  //nums.get(i);
}

//for each loop
for (int i: nums){
  //do stuff with i
}

HashMap:

Map<String,String>myMap=new HashMap<>();

// add key
myMap.put("Hadi","21");

// get the value of the key
myMap.get("Hadi");

// remove the key
myMap.remove("Hadi");

// clear whole Map
myMap.clear();

// get the size
myMap.size();

// Different way of loop
for (String name: myMap.keySet()){
  System.out.println(age);
}

for (String age: myMap.values()){
  System.out.println(age);
}

for(Map.Entry<String,String>entry:myMap.entrySet()){
  String key=entry.getKey();
  String value=entry.getValue();
}

Example:

class Trainer{
    private String id;
    private String name;

  public  Trainer(String id, String name)
	{
		this.id = id;
		this.name = name;
	}
	public String getID() { return id; }
	public String getName() { return name; }
}
public static void main(String[]args){

  Map<String,Trainer> train=new HashMap<>();

  train.put("red",new Trainer("40","Hadi"));
  train.put("blue",new Trainer("401","Had"));
  train.put("Yellow",new Trainer("402","Ha"));
  train.put("black",new Trainer("403","H"));

  for(Map.Entry<String,Trainer>data:train.entrySet()){

    System.out.println("Color: "+(String)data.getKey()+" id: "+(String)data.getValue().getID());
  }

}
}

Overriding:

toString():

  public String toString(){ return name;}