This document provides an overview of key concepts in Java for Android development including object-oriented programming concepts, primitive data types, operators, control flow statements, classes, exceptions, and collections. It also discusses nested classes, anonymous classes, enums, and extra topics like reflection and threading. The document emphasizes practicing these concepts in any subject domain using inheritance, abstract classes, and interfaces.

1. Java for Android
Development

2. Object-Oriented Programming Concepts

3. Comments
/* multiline
comment */
// singleline comment
/** Description
*
* @param input
* @return output
*/

4. Primitive Data Types
● byte (8-bit signed integer between -128 and 127)
● short (16-bit signed integer between -32,768 and 32,767)
● int (32-bit signed integer between -2,147,483,648 and 2,147,483,647)
● long (64-bit signed integer between -9,223,372,036,854,775,808 and
9,223,372,036,854,775,807)
● float (32-bit floating point number)
● double (64-bit floating point number)
● boolean (true and false)
● char (single 16-bit Unicode character)

5. Operators

6. If
if (a > 0) {
// ...
} else if (a == 0) {
// ...
} else {
// ...
}

7. boolean a;
if (a == true) ...
if (a == false) ...
if (a) ...
if (!a) ...

8. switch
switch (code) {
case 200:
// ...
break;
case 404:
// ...
break;
default:
// ...
break;
}

9. Loops
● while
● do-while
● for
● for-each

10. while
int n = 10
while (n > 0) {
n--;
}

11. do
n = 10;
do {
n--;
} while (n > 0);

12. for
for (int i = 0; i < 100; i++) {
//...
}

13. for-each
for (Object o : objects) {
System.out.print(o.toString());
}

14. Branching statements
● break
● continue
● return

15. Arrays

16. String
● Immutable
● StringBuilder
● Никогда не
проверяйте
равенство строк с
помощью == !!!

18. Class
● class MyClass {...}
● instance (object)
● fields
● methods
● inner and nested classes
● this
● final
● static

20. import
● import java.util.List;
● import org.apache.http.HttpEntity;
● import org.json.JSONObject;
● import android.content.SharedPreferences;
● import com.inflow.model.Feed;
● import java.io.IOException;

21. Access Modifiers

22. Inheritance
● class MyClass extends BaseClass {...}
● super
● @Override

24. Abstract Classes and Methods
● abstract class MyClass {...}
● abstract void myMethod {...}

27. Interfaces
● interface
● class MyClass implements MyInterface

29. java.lang.Object
○ public String toString();
○ public boolean equals(Object obj);
○ public native int hashCode();
○ protected native Object clone() throws CloneNotSupportedException;
○ protected void finalize() throws Throwable;
○ public final native Class<?> getClass();
○ public final native void notify();
○ public final native void notifyAll();
○ public final native void wait(long timeout) throws InterruptedException;
○ public final void wait(long timeout, int nanos) throws InterruptedException;
○ public final void wait() throws InterruptedException;

30. equals()
● Рефлексивность: x.equals(x) -> true при x не null;
● Симметричность: x.equals(y) <- -> y.equals(x) при x,y не null;
● Транзитивность: x.equals(y), y.equals(z) -> x.equals(z) при x,y,z не null;
● Непротиворечивость (consistency) «одинаковых» вызовов;
● x.equals(null) – всегда false (при x не null).

31. hashCode()
● Метод hashCode() надо переопределять в каждом классе,
переопределяющем метод equals().
● Контракт метода hashCode():
■ Непротиворечивость (consistency), «осмысленно»
возвращает то же число;
■ Равные по equals() объекты дают равные значения
hashCode();

32. Nested Classes
class OuterClass {
...
static class StaticNestedClass {
...
}
}
MyOuterClass.MyStaticNestedClass myObject = new
MyOuterClass.MyStaticNestedClass();

33. Inner classes
class OuterClass {
...
static class StaticNestedClass {
...
}
class InnerClass {
...
}
}
OuterClass.InnerClass innerObject = outerObject.new
InnerClass();

34. Anonymous classes
button.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
//...
}
});

35. Enums
public enum Day {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
THURSDAY, FRIDAY, SATURDAY
}

36. Exceptions
● try
● catch
● finally
● throw

37. Collections
● List
● Set
● Map
● Queue
● Stack
● ...

38. Extra topics
● Reflection
● Threading
● Generics

39. Literature
● Cay Horstmann Core Java
● Bruce Eckel Thinking in Java

40. Practice
● любая предметная область
● наследование
● абстрактный класс
● интерфейс