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abstract class

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Java

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Mar 1, 2020

Cards (32)

Section 1

(32 cards)

abstract class

Front

1. inheriting class should implement the abstract method 2. Abstract classes offer default functionality for the subclasses 3. Abstract class cannot be instantiated 4. Can have fields declared

Back

Primitive types

Front

Data types that are not objects (Boolean,byte,short,int,float,double)

Back

primitive variables,local variables are stored and methods

Front

in Stack

Back

If no constructor is provided

Front

Default constructor creates empty object structure without initialized values. Object properties are null

Back

StackTrace

Front

a report of the function calls made by a program during debugging.

Back

HashMap contains key

Front

map.ContainsKey("Item");

Back

Component

Front

class that has attributes with member methods. Member methods may use attributes to fullfill business logic

Back

Interface name convention

Front

Names usually starts with "Can" or ends with "able"

Back

When to use composition?

Front

in case when class wants to use only few behaviours

Back

Pojo Plain Old Java Objects

Front

ordinary Java object that not bound by any special restriction

Back

Java beans

Front

class that contains only attributes with getters and setters

Back

valueOf()

Front

Converts primitive data type to String

Back

Generic

Front

Classes, Interfaces, methods in which type of data is specified as parameter. Allows to create single class that automatically works with different data type. Generics works only with object

Back

Byte code

Front

machine language of JVM

Back

composition

Front

Has-A relation. class will hold other classes reference as attributes

Back

HashMap iterate over values

Front

for(String i: map.values()) { ... }

Back

StringBuffer

Front

Mutable string object that can be change

Back

equals() vs ==

Front

Back

Can constructor be inherited?

Front

No, constructor cannot be inherited.

Back

Upcasting

Front

Assigning an object of a derived class type to a variable of an ancestor class

Back

Varargs ( Arbitrary Number of Arguments )

Front

zero or more String objects arguments. he argument(s) passed in this way is always an array public void myFunc(String... s);

Back

Collection cannot contain

Front

Primitive types, instead use Class wrappers ( Integer, Double)

Back

Functional Interface

Front

Interface containing only one method and often used with Lambdas. Marking annotation: @FunctionalInterface public interface IntToLongFunc() { long applyAsLong(int value); }

Back

equals

Front

compare none primitive objects (strings, array elements)

Back

Where Object is located

Front

in Heap

Back

Add value to HashMap

Front

items.put("Item", 5);

Back

HashMap

Front

storing Key & value pairs HashMap<String, Integer> items = new HashMap<>()

Back

String object

Front

stored in string constant pool

Back

method overloading

Front

The ability to define two or more different methods with the same name but different method signatures.

Back

Interface

Front

1. interface methods cannot have a body only signature 2. When you implement interface you must use it 3. Cannot contain instance variables, but, they can contain public static final variables 4. Allows you to separate the definition of a method from the inheritance hierarchy 5. Can extend another interface

Back

Multiple Constructors

Front

A class can have multiple constructors, as long as their signature (the parameters they take) are not the same.

Back

3 tier architecture

Front

MVC 1. Presentation Layer (UI, View) 2. Business Logic Layer 3. Data Layer (Model)

Back