Initialize variable

Initialize Member Variables(Class variable, Instance variable)

Initializing order

1. cv

2. iv

1. automatic : 0

2. =

3. {} : class variable(static) => static {...}, instance variable => constructor

Initialize local variable before use!(ESSENTIAL)

member variable(instance variable, class(static) variable)) is initialized automatically.

1. Initialize with =

class Car {

    int door = 4;
    //Engine e;
    Engine e = new Engine();//create object and put into e 
    

2. initialize with {..}

initialize instance : {...}

initialize cv(classs variable(static)) : static {...}

class StaticBlockTest {
    static int[] arr = new int[10];
    //initialize static variable(class variable)
    static {
        for(int i = 0; i < arr.length;i++) {
            arr[i] = (int)(Math.random()*10)+1;
        }
    }
}

3. initialize (instance) with constructor

class Car {
    Car(String color, String gearType, int door) {
        this.color = color;
        this.gearType = gearType;
        this.door = door;
    }
...
}