Variables

String = null; (programmed to nothing)

float = 0.0;

booleans = false;

int/char = 0;

->Declared in class but not in method

->Have default value

class book{ 
private String name; (null)
private int size; (defalut value size = 0)
}

->Declared within method

->Not have default value (not initialized & should be initialized before used)

class add{
void result(){
 int a; 
 int b;
 //a and b should have value otherwise it won't compile gives error.
 int result = a + b;
  }
}

*Primitive Type:-

->two variable is same if bit pattern same

->size not matter

int a = 3;
 byte b = 3;
 if(a == b){//true}

*Reference type

->if two reference variable refer to same object

 Dog a = new Dog();
 Dog b = new Dog();
 Dog c == a;

 if(a == b){//false};
 if(c == a){//true};
 if(b == c){//false};

Note:

->use == for comparing two primative or reference variable if refers to same object

->Use .equals() for two different object if equal (ex. if two String object have value "Fred").

Prnc Tech