Knowlesge - exceptions

Facts:

1. 
   

Thread pool : Callable, Runnable, Executors

package com.areo;

import java.util.ArrayList;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class Main {

	public static void main(String[] args) {
		executorWithRunnable();
		executorWithCallable();
	}

	private static void executorWithCallable() {

		ExecutorService pool = Executors.newFixedThreadPool(10);
		
		ArrayList<Future<Integer>> list 
			= new ArrayList<Future<Integer>>();
		
		for (int i = 0; i < 300; i++) {
			Future<Integer> submit = pool.submit(new MyCallable());
			list.add(submit);
		}
		
		//father results
		int result = 0;
		for (Future<Integer> future : list) {
			try {
				result += future.get();
			} catch (InterruptedException e) {
			} catch (ExecutionException e) {
			}
		}
		
		//result is 300
		System.out.println("Result: " + result);
		
	}

	private static void executorWithRunnable() {
		ExecutorService pool = Executors.newFixedThreadPool(10);
		
		for (int i = 0; i < 300; i++) {
			pool.execute(new MThread());
		}
		
		pool.shutdown();
	}

	//callable
	static class MyCallable implements Callable<Integer>{

		
		public Integer call() throws Exception {
			
			System.out.println("Calling!");
			return 1;
		}
		
	}
	
	//runnable
	static class MThread implements Runnable{

		public void run() {
			long id = Thread.currentThread().getId();
			System.out.println(String.format("Thread id = %d", id));
		}
		
	}
}

Guava - EventBus example

package com.areoit.guava.eventbus;

import org.junit.Test;
import static org.junit.Assert.assertEquals;

import com.google.common.eventbus.EventBus;
import com.google.common.eventbus.Subscribe;

public class EventBusIntegerEventsTests {
 
 private static final String EVENT_BUS_ID = "numbers";

 /**
  * Case:
  *  + one listener
  *  + listener subcribe for Integer event
  *  + listener subcribe for Number event
  *  + REMEMBER: Integer IS-A Number
  */
 @Test
 public void oneIntegerEventTwoSubscribingMethod() {
 
  IntegerListener listener = new IntegerListener();
  Integer integerEvent = Integer.MAX_VALUE;
  
  EventBus eventBus = new EventBus(EVENT_BUS_ID);
  eventBus.register(listener);  
  eventBus.post(integerEvent);
  
  //check event counters
  int integerCount 
   = listener.getIntegerEventCount();
  
  int numberCount 
   = listener.getNumberEventCount();
  
  assertEquals(1, integerCount);
  assertEquals(1, numberCount);
 }
 

 class IntegerListener  {

  private int integerEventCount = 0;
  private int numberEventCount = 0;
   
  @Subscribe
  public void onIntegerEvent(Integer event) {
   ++integerEventCount;
  }
  
  @Subscribe
  public void onNumberEvent(Number event) {
   ++numberEventCount;
  }

  public int getIntegerEventCount() {
   return integerEventCount;
  }

  public int getNumberEventCount() {
   return numberEventCount;
  }
 }
 
 
}

Guava - Functions + composition

public class FunctionsTests {
 
 @Test
 public void Functions_converter_example() {
  
  Function stringToInteger = new Function() {

   @Override
   public Integer apply(String input) {
    return Integer.valueOf(input);
   }
  };
  
  Function integerToLong = new Function\() {
   @Override
   public Long apply(Integer input) {
    return Long.valueOf(input.longValue());
   }
  };
  
  Function stringToLong 
   = Functions.compose(integerToLong, stringToInteger);
  
  Long actual = stringToLong.apply("5");
  Long expected = 5L;
  
  assertEquals(expected, actual);
 }
}

Guava - Joiner

import org.junit.Test;

import com.google.common.base.Joiner;

public class Collections {

 @Test
 public void Joiner_on_list_with_one_null_value() {
  
  String actual 
   = Joiner
    .on(",")
    .skipNulls()
    .join("one",null,"two");
  
  assertEquals("one,two", actual);
 }
 
 @Test
 public void Joiner_on_map() {
  
  Map map = new HashMap();
  map.put("k1", "v1");
  map.put("k2", "v2");

  String actual 
   = Joiner
    .on(",")
    .withKeyValueSeparator(" => ")
    .join(map);
  
  assertEquals("k1 => v1,k2 => v2", actual);
 }

}

Inner class

1. Klasy inner nie mogą mieć czegokolwiek static!
2. MyOuter mo = new MyOuter(); // gotta get an instance!
   MyOuter.MyInner inner = mo.new MyInner();
3. Instancja poza Outer class przez instancje.new Inner()
4. IInstancja z klasy Outer Inner() normalnnie
5. Nie mozna tworzyc Inner w statycznych metodach outer!!
6. this w metodach Inner class odności sie do obiektu Inner !
7. Outer.this odnosi sie wiadomo ( z poziomu metod Inner)
8. Modyfikatory przy class Inner{} => public,protected,private ,final,abstract,static,strictfp //jak normalny member klasy Outer!!
9. Local method class może być instance tylko w tej metodzie!
10. Local method class może dobrać sie do Outer private members!
11. Local method class nie może dostać sie do zmiennych w tej metodzie(nie fianl)!
12. Local method class może dostać sie do zmiennych fonal w tej metodzie!!
13. Local method class może być zonaczona jako final!! ( tak jak zmienna lokalna ,zasady)
14. Local method class w metodzie statycznej ma tylko dostęp do zmiennych statycznych!! i nie ma dostępy do zmiennych outerClass!!
15. Pamiętaj średniku po definicji klasy anonymous!!
16. Klasa anonymous raczej overriding method niż dodaje ( problem z widzeniem nowej innej metody)
17. interface cannot be in method :(
18. Anonymous class moze implements tylko 1 interfejs!!
    

Generics

1. List oznacza każdą listę czegokolwiek
2. List foo = new ArrayList();// bad!
3. 1) List list = new ArrayList(); //OK
   2) List aList = new ArrayList();//OK
   3) List foo = new ArrayList(); //BAD
   4) List cList = new ArrayList();//BAD
   5) List bList = new ArrayList(); //OK
   6) List dList = new ArrayList(); //BAD