書籍およびドキュメントのJavaの例

書籍とドキュメントで構成されたサンプルのセット。 PDF +ソース

padaboo IB AleksandrovによるJavaの書籍とインターネットのサンプル







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Basics Data types. package basics; /** * * @author Padaboo IB Aleksandrov */ public class DataTypes { public static void main(String[] args) { DataTypes app = new DataTypes(); //int 4byte -2147483648 2147483648 int i = 1; //short 2byte -32768 32767 short s = 1; //long 8byte -9223372036854775808 -9223372036854775807 long l = 1; //byte 1byte -128  127 byte b = 1; //float 4byte +-3,40282347E+38F float f = 0.1f; //double 8byte +-1,7976931348623157E+308F double d = 0.2f; //char char c = 'd'; //boolean true false logical 1/0 boolean bool = true; } //public static constatn available in any method in other classes //a constant can not be changed public static final double con = 0.3f; } Math package basics; /** * https://docs.oracle.com/javase/tutorial/java/data/beyondmath.html * @author padaboo IB Aleksandrov */ public class JavaMath { public static void main(String[] args) { /** Math.abs (n) - returns the unit number n. Math.round (n) - returns an integer closest to a real number n (rounds n). Math.ceil (n) - returns the closest number to the number n to the right of zero fractional part (eg, Math.ceil (3.4) returns a result of 4.0). Math.cos (n), Math.sin (n), Math.tan (n) - trigonometric function sin, cos tg and the argument n, indicated in radians. Math.acos (n), Math.asin (n), Math.atan (n) - inverse trigonometric functions return the angle in radians. Math.toDegrees (n) - a measure of returns-degree angle in radians n. Math.toRadians (n) - returns radian measure of an angle in degrees n. Math.sqrt (n) - returns the square root of n. Math.pow (n, b) - returns the value of the power function of degree nb, the base and the exponent may be real. Math.log (n) - returns the natural logarithm of n. Math.log10 (n) - returns the logarithm of n. */ System.out.println(Math.abs(-2.33)); System.out.println(Math.round(Math.PI)); System.out.println(Math.round(9.5)); System.out.println(Math.round(9.5-0.001)); System.out.println(Math.ceil(9.4)); double c = Math.sqrt(3*3 + 4*4); System.out.println(c); double s1 = Math.cos(Math.toRadians(60)); System.out.println(s1); } } Operations package basics; /** * * @author Padaboo IB Aleksandrov */ public class Operations { public static void main(String[] args) { Operations app = new Operations(); /** * + sum * - subtraction * / division * * multiplication * % remainder of the division */ int x = 1; x = x + x; System.out.println(x); //2 //x+1 ++x; System.out.println(x); //3 x += 2; System.out.println(x); //5 /** * Logical operations * == equally * != not equally * <= less or equal * => more or equal * < less * > more * && and * || or */ boolean result = (x != 1); System.out.println(result); //true result = ((x != 1) && (x == 2)); System.out.println(result); //false //ternar (condition) ? expression_1 : expression_2 //if the expression is true if the first part is done there is no second result = x>3 ? true : false; System.out.println(result); /** * byte operations * & byte and * | byte or * ^ excluding or * ~ not * >> bit shift to the right * << bit shift to the left */ /** * Priority * [] () from right to left * !~++--+()new from right to left * * / % from left to right * + - from left to right * << >> >>> from left to right * < <= > >= instanceof from left to right * == != from left to right * & from left to right * ^ from left to right * | from left to right * && from left to right * || from left to right * ?: from right to left * = += -= *= /= %= |= ^= <<= >>= >>>= from right to left */ // null - empty field // nan - not a number } } Constructions package basics; /** * * @author Padaboo IB Aleksandrov */ public class Constructions { //public, visible inside and outside public int pub = 1; //private, visible inside private int pri = 2; //protected, visible inside and in child class protected int pro = 3; //public static varible public static int staticVar = 4; //constant public final static int finalVar = 4; //enum is used as a constant enum Modifier { PUBLIC, PROTECTED, PRIVATE, ABSTRACT, STATIC, FINAL, TRANSIENT, VOLATILE, SYNCHRONIZED, NATIVE, STRICTFP; } public static void main(String[] args) { //local varible of method (funttion) int localVarible = 0; //create exemplar of class (object) constructions Constructions constructions = new Constructions(); //if condition if(1 == 1){ //true } else { //false } //else if if (false){ }else if (false){ }else { //do } //for: repeating cycle with the condition 1 for(int i=1; i<5; i++){ System.out.println("i is: " + i); } //for: repeating cycle with the condition 2 int[] numbers = {1,2,3,4,5,6,7,8,9,10}; for (int item : numbers) { System.out.println("i is: " + item); } //while true int n = 5; while (n > 0) { System.out.println("while " + n); n--; } //do while true int i = 0; do{ System.out.print ("while " + ++i); } while (i < 10); //continue skip iteration/next //new create a new object String s = new String(); //selection operator int month = 3; switch (month) { case 1: s = "1"; break; case 2: s = "2"; break; case 3: s = "3"; break; case 4: s = "4"; default: break; } //print case result System.out.println(s); //private varible System.out.println(constructions.pri); //public varible System.out.println(constructions.pub); //protected varible System.out.println(constructions.pro); System.out.println(staticVar*2); //call function from object System.out.println(constructions.func()); //call overload function func with 2 arguments System.out.println(constructions.func(2,2)); //call enum Modifier Modifier variableModifier = Modifier.PUBLIC; System.out.println(variableModifier); } /** * private function return type int, no arguments */ private int func(){ //do return 128; } /** * function overloading with 2 arguments * @param a * @param b * @return int */ private int func(int a,int b){ return a*b; } } Strings package basics; /** * * @author Padaboo IB Aleksandrov */ public class Strings { public static void main(String[] args) { String j = "jmonkey"; String e = "engine"; //concatenation System.out.println(j+3); //jmonkey3 System.out.println(j + " " + e); //equals == System.out.println(j.equals("jmonkey")); //length System.out.println(j.length()); //substring start end System.out.println(j.substring(0,3)); //jmo //first symbol char first = j.charAt(0); //j System.out.println(first); char arr[] = {'j','m','3'}; String fromchar = new String(arr); System.out.println(fromchar); //JDK API String https://docs.oracle.com/javase/7/docs/api/java/lang/String.html } } Arrays package basics; import java.util.ArrayList; /** * Java arrays * @author Padaboo IB Aleksandrov */ public class Arrays { public static void main(String[] args) { //create array of integer size 3 int[] a = new int[3]; a[0] = 1; a[1] = 2; a[2] = 3; int[] b = {1,2,3}; for(int j = 0; j <= b.length - 1; j++) { System.out.println(b[j]); } //multidimensional array int[][] ab = new int[6][4]; //int[][] ab = {{2,3},{2,2}}; for(int i=0; i<ab.length; i++) { for(int j=0; j<ab[i].length; j++) { ab[i][j] = (int)(Math.random()*10); } } //array of objects Car[] cars = new Car[10]; //array list ArrayList<Car> carList = new ArrayList<Car>(); int i = 0; //add objects to array list while(i< 3){ carList.add(new SportCar()); } Car[] carsArray = new Car[carList.size()]; carList.toArray(carsArray); //add(n,e); //remove(n); //https://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html } } Collections package basics; import java.util.HashMap; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.LinkedList; import java.util.List; import java.util.Map; import java.util.Map.Entry; import java.util.Queue; import java.util.Set; import java.util.TreeMap; /** * LinkedList HashMap LinkedHashMap TreeMap * https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html * @author Padaboo IB Aleksandrov */ public class Collections { public static void main(String[] args) { Collections app = new Collections(); //app.LinkedListExample(); //app.HashMapExample(); //app.LinkedHashMap(); //app.TreeMapExample(); app.QueueExample(); } private void LinkedListExample(){ //Java LinkedList List<String> list = new LinkedList<String>(); list.add("player 1"); list.add("player 2"); list.add("player 3"); Iterator iter = list.iterator(); while(iter.hasNext()){ System.out.println(iter.next()); } for(int num=0; num<list.size(); num++){ System.out.println(list.get(num)); } for (Iterator<String> it = list.iterator(); it.hasNext();) { String str = it.next(); System.out.println(str); } list.get(0); list.set(1,"Monster"); list.remove(0); list.size(); //https://docs.oracle.com/javase/7/docs/api/java/util/LinkedList.html } private void HashMapExample(){ //java HashMap Example Map<String, Car> hashmap = new HashMap<String, Car>(); hashmap.put("id1", new SportCar()); hashmap.put("id2", new SportCar()); hashmap.put("id3", new SportCar()); SportCar iterCar; for (Map.Entry entry : hashmap.entrySet()) { iterCar = (SportCar)entry.getValue(); System.out.println("key: " + entry.getKey() + " val: "+ iterCar.getSpeed()); } } private void LinkedHashMap(){ //Java LinkedHashMap Example LinkedHashMap<Integer, String> map = new LinkedHashMap<Integer, String>(); map.put(1, "Java"); map.put(2, "Jmonkey"); map.put(3, "3d"); map.put(4, "Convas"); map.put(5, "ClientServer"); //map.get(4); Set set = map.entrySet(); Iterator iterator = set.iterator(); Map.Entry me; while(iterator.hasNext()) { me = (Map.Entry)iterator.next(); System.out.println("key: "+ me.getKey() + " val: "+me.getValue()+"\n"); } } private void TreeMapExample(){ TreeMap<Integer, String> tmap = new TreeMap<Integer, String>(); tmap.put(1, "Blender"); tmap.put(3, "Ogre3D"); tmap.put(70,"Animation"); tmap.put(4, "Shaders"); for (Entry<Integer, String> entry : tmap.entrySet()) { System.out.println(entry.getKey() + " - " + entry.getValue()); } } private void QueueExample(){ Queue<String> qe=new LinkedList<String>(); qe.add("Java Oracle"); qe.add("Ubuntu Linux"); qe.add("Convas 3d"); for (String iteratorValue : qe) { System.out.println("Queue Next Value :"+iteratorValue); } } } Try cahtch package basics; import java.util.logging.Level; import java.util.logging.Logger; /** * https://docs.oracle.com/javase/tutorial/essential/exceptions/ * @author padabo IB Aleksandrov */ public class ExceptionTryCatchFinally { public static void main(String[] args) { try{ throw new Exception("Simple Exception"); }catch(Exception e){ Logger.getLogger(IO.class.getName()).log(Level.SEVERE, null, e); System.out.println(e.getMessage()); }finally{ System.out.println("Finally"); } } } Objects Abstarct car package basics; /** * Abstract class (have abstract methods) * @author Padaboo IB Aleksandrov */ public abstract class Car{ protected int speed; protected String color; /** * constructor */ public Car(){ speed = 50; } /** * overload * @param color */ public Car(String color){ this.color = color; } /** * A common method for all heirs */ public void drive(){ //do drive } /** * a method that must be implemented in all heirs */ abstract boolean painting(String newColor); /** * * @return int speed */ public int getSpeed(){ return speed; } /** * a method that must be implemented in all heirs */ abstract void acceleration(int a); } Sport car /* */ package basics; /** * Heir class abstract class car * @author Padaboo IB Aleksandrov */ public class SportCar extends Car { @Override boolean painting(String newColor) { color = newColor; return true; } public void acceleration(int a) { speed = speed * a; } } /* */ package basics; /** * Heir class abstract class car * @author Padaboo IB Aleksandrov */ public class SportCar extends Car { @Override boolean painting(String newColor) { color = newColor; return true; } public void acceleration(int a) { speed = speed * a; } } package basics; /** * Objects abstract extends protected * @author padaboo IB Aleksandrov */ public class Objects { public static void main(String[] args) { Car sportCar = new SportCar(); System.out.println(sportCar.getSpeed()); sportCar.acceleration(20); System.out.println(sportCar.getSpeed()); } } Reflections package basics; import java.lang.reflect.Field; /** * * @author padaboo IB Aleksandov */ public class Reflection { public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException { //get class name SportCar sc = new SportCar(); String name = sc.getClass().getName(); System.out.println(name); //object from class name Object rsc = (Object) Class.forName(name).newInstance(); System.out.println(rsc.toString()); //get class Class csc = SportCar.class; System.out.println(csc); //get fields of super class Field[] fields = SportCar.class.getSuperclass().getDeclaredFields(); for (Field field : fields) { System.out.println(field.getName()); } //https://docs.oracle.com/javase/tutorial/reflect/ } } Parametrization package basics; /** * Java Parametrizations generic inner class example * @author padaboo IB Aleksandrov */ public class Parametrization{ //https://docs.oracle.com/javase/tutorial/extra/generics/methods.html public static void main(String[] args) { Parametrization app = new Parametrization(); app.genericTest(); } private void genericTest(){ GenericObj<String,Car> g = new GenericObj<String,Car>("Test",new SportCar()); } class GenericObj<String,T extends Car> { public String name; public T car; private GenericObj(String str, T carObj) { car = carObj; name = str; } } } Class path package basics; import java.io.File; /** * http://docs.oracle.com/javase/tutorial/essential/environment/sysprop.html * @author padaboo IB Aleksandrov */ public class ClassPath { public static void main(String[] args) { System.getProperty("java.class.path"); String classpath = System.getProperty("java.class.path"); String[] classpathEntries = classpath.split(File.pathSeparator); for(String s: classpathEntries){ System.out.println(s); } } } IO /* <?xml version="1.0" encoding="UTF-8"?> <root> <rows> <item name="player1" level="20" /> <item name="player2" level="15" /> <item name="player3" level="10" /> </rows> <system fps="60"/> </root> */ package basics; import java.io.BufferedReader; import java.io.File; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; /** * https://docs.oracle.com/javase/tutorial/essential/io/scanning.html * IO Java read file write file sample; * @author Padaboo IB Aleksandrov */ public class IO { String fileName = "iotest.xml"; String content; String absoluteFilePath; String workingDirectory; public static void main(String[] args) throws IOException { IO app = new IO(); app.workingDirectory = app.getworkingDirectory(); app.absoluteFilePath = app.workingDirectory + app.fileName; app.content = app.readFile(app.absoluteFilePath); app.content += "append"; app.writeFile(app.absoluteFilePath,app.content); } private String getworkingDirectory(){ return System.getProperty("user.dir") + File.separator + "src"+File.separator+ "basics"+File.separator; } private String readFile(String path) throws IOException{ BufferedReader br = new BufferedReader(new FileReader(path)); StringBuilder sb = new StringBuilder(); String line = br.readLine(); while (line != null) { sb.append(line); sb.append(System.lineSeparator()); line = br.readLine(); System.out.println(line); } br.close(); return sb.toString(); } private void writeFile(String path,String str) throws IOException{ File file = new File(path); FileWriter writer = new FileWriter(file); writer.write(str); writer.flush(); writer.close(); } } XML /* <?xml version="1.0" encoding="UTF-8"?> <root> <rows> <item name="player1" level="20" /> <item name="player2" level="15" /> <item name="player3" level="10" /> </rows> <system fps="60"/> </root> */ package basics; import java.io.File; import java.io.IOException; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.xml.sax.SAXException; /** * https://docs.oracle.com/javase/7/docs/api/javax/xml/xpath/package-summary.html * https://docs.oracle.com/javase/tutorial/jaxp/sax/parsing.html * Xml Xpath sample * @author padaboo IB Aleksandrov */ public class XmlSample { public static void main(String[] args) throws IOException, ParserConfigurationException, SAXException { String filePath = XmlSample.getworkingDirectory() + "iotest.xml"; DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); factory.setNamespaceAware(true); DocumentBuilder builder; org.w3c.dom.Document doc = null; builder = factory.newDocumentBuilder(); doc = (org.w3c.dom.Document) builder.parse(new File(filePath)); NodeList ltemsList = doc.getElementsByTagName("item"); for(int i=0; i<ltemsList.getLength() ; i++) { Node itemNode = ltemsList.item(i); System.out.println(itemNode.getAttributes().getNamedItem("level").getNodeValue()); } } public static String getworkingDirectory(){ return System.getProperty("user.dir") + File.separator + "src"+File.separator+ "basics"+File.separator; } } System Command line package sys; /** * https://docs.oracle.com/javase/tutorial/essential/environment/cmdLineArgs.html * @author padaboo IB Aleksandrov */ public class CommandLineSample { public static void main(String[] args){ if (args.length > 0) { for (String s: args) { System.out.println(s); } } } } Execute package sys; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; /** * https://docs.oracle.com/javase/7/docs/api/java/lang/Runtime.html * @author padaboo IB Aleksandrov */ public class ExecuteSample { public static void main(String[] args) throws IOException, InterruptedException { Process p = Runtime.getRuntime().exec("pwd"); p.waitFor(); BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream())); String line = ""; while ((line = reader.readLine()) != null) { System.out.println(line); } } } Key press package sys; import java.util.Scanner; /** * https://docs.oracle.com/javase/tutorial/essential/io/scanning.html * @author padaboo IB Aleksandrov */ public class InScannerKeyPress { public static void main(String[] args) { Scanner keyboard = new Scanner(System.in); boolean exit = false; while (!exit) { String input = keyboard.nextLine(); if(input != null) { System.out.println("Your input is : " + input); if ("quit".equals(input)) { exit = true; } else if ("x".equals(input)) { } } } keyboard.close(); } } Native Sample package sys; /** * * https://www3.ntu.edu.sg/home/ehchua/programming/java/JavaNativeInterface.html * https://en.wikipedia.org/wiki/Java_Native_Interface * @author padaboo IB Aleksandrov */ public class NativeSample { public native void displayHelloWorld(); static{ System.loadLibrary("hello"); } public static void main(String[] args){ /** javac NativeSample.java $ javah -classpath . NativeSample $ gcc -shared -fPIC -I $JAVA_HOME/include -I $JAVA_HOME/include/linux Hello.cpp -o hello.so $ java -classpath . -Djava.library.path=. HelloWorld Hello World! */ new NativeSample().displayHelloWorld(); } } /** #include "HelloJNICppImpl.h" #include <iostream> using namespace std; void sayHello () { cout << "Hello World from C++!" << endl; return; } */ /** #ifndef _HELLO_JNI_CPP_IMPL_H #define _HELLO_JNI_CPP_IMPL_H #ifdef __cplusplus extern "C" { #endif void sayHello (); #ifdef __cplusplus } #endif #endif */ Threads Thread package threads; /** * https://docs.oracle.com/javase/7/docs/api/java/lang/Thread.html * Java Threads * @author Padaboo IB Aleksandrov */ public class ThreadSample{ public static void main(String[] args) { ThreadSample app = new ThreadSample(); app.threadRun(); } class MyThread extends Thread{ @Override public void run() { System.out.println("Run"); } } private void threadRun(){ MyThread t = new MyThread(); t.start(); } } Thread Sleep package threads; import java.util.logging.Level; import java.util.logging.Logger; /** * https://docs.oracle.com/javase/tutorial/essential/concurrency/sleep.html * Java thread sleep * @author Padaboo IB Aleksandrov */ public class ThreadSleepSample { public static void main(String[] args) { ThreadSleepSample app = new ThreadSleepSample(); app.threadSleepTest(); } private void threadSleepTest(){ Runnable r; r = new Runnable() { public void run() { for (int i = 0; i < 9; i = i + 1){ try { System.out.println("Run " + i); Thread.sleep(500); } catch (InterruptedException ex) { Logger.getLogger(ThreadSleepSample.class.getName()).log(Level.SEVERE, null, ex); } } } }; Thread t = new Thread(r); t.start(); } } Thread Lock package threads; import java.util.concurrent.TimeUnit; import java.util.concurrent.locks.Lock; /** * https://docs.oracle.com/javase/tutorial/essential/concurrency/newlocks.html * Java lock sample * @author padaboo IB Aleksandrov */ public class ThreadLock implements Runnable{ private Lock lock; public static void main(String[] args){ ThreadLock app = new ThreadLock(); } @Override public void run() { try { if(lock.tryLock(10, TimeUnit.SECONDS)){ //do } } catch (InterruptedException e) { e.printStackTrace(); }finally{ //unlock lock.unlock(); } } } Thread Local package threads; /** * Java ThreadLocal example * https://docs.oracle.com/javase/7/docs/api/java/lang/ThreadLocal.html * @author Padaboo IB Aleksandrov */ public class ThreadLocalSample implements Runnable { ThreadLocal<String> str = new ThreadLocal<String>(){ @Override protected String initialValue(){ return new String("Test"); } };; public static void main(String[] args){ ThreadLocalSample app = new ThreadLocalSample(); Thread t = new Thread(app); t.start(); } public void run() { System.out.println(str.get()); } } Daemon thread package threads; /** * https://docs.oracle.com/javase/7/docs/api/java/lang/Thread.html * Java daemon thread * @author Padaboo IB Alelsandrov */ public class DaemonThread extends Thread{ public static void main(String[] args) throws InterruptedException { DaemonThread t = new DaemonThread(); t.setDaemon(true); t.start(); try { Thread.sleep(3000); } catch (InterruptedException x) {} } @Override public void run() { while (true) { System.out.println("Daemon Run "); try { sleep(500); } catch (InterruptedException e) { // handle exception here } } } } Runnable package threads; /** * Java runnable threads * @author padaboo IB Aleksandrov */ public class RunnableSample implements Runnable{ public static void main(String[] args) { RunnableSample run = new RunnableSample(); Thread t = new Thread(run); t.start(); } public void run() { int i = 1; while(i<=10){ System.out.println(i); i++; } } } Runanble handler package threads; /** * Java Runnable handler * @author Padaboo IB Aleksandrov */ public class RunnableHandler { public static void main(String[] args) { RunnableHandler app = new RunnableHandler(); app.hadlerTest(); } public void hadlerTest(){ Runnable handler = new Runnable(){ public void run() { System.out.println("Run"); } }; Thread t = new Thread(handler); t.start(); } } Thread isInterrupted package threads; /** * https://docs.oracle.com/javase/tutorial/essential/concurrency/interrupt.html * @author padaboo IB Aleksandrov */ public class ThreadInterrupted extends Thread{ public static void main(String[] args){ ThreadInterrupted app = new ThreadInterrupted(); app.start(); } public void run( ) { int i = 0; while (!isInterrupted( )) { System.out.println("i:"+i); i++; } } } Thread executors package threads; import java.util.concurrent.Executor; /** * https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/Executor.html * Java Thread Executors * @author padaboo IB Aleksandrov */ public class ExecutorsSample { public static void main(String[] args) { ExecutorsSample app = new ExecutorsSample(); app.executorsTest(); } private void executorsTest(){ Executor executor = new Executor() { public void execute(Runnable command) { command.run(); } }; Runnable command = new Runnable() { public void run() { System.out.println("Run"); } }; executor.execute(command); } } Thread executors services package threads; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; /** * Java Executor ExecutorService * https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ExecutorService.html * @author Padaboo IB Aleksandrov */ public class ExecutorsServicesSample { ExecutorService pool = Executors.newFixedThreadPool(2); public static void main(String[] args) { ExecutorsServicesSample app = new ExecutorsServicesSample(); app.ExecutorsServicesTest(); } private void ExecutorsServicesTest(){ pool.execute(new Handler(1)); pool.execute(new Handler(2)); pool.shutdown(); } class Handler implements Runnable { private final int number; Handler(int number) { this.number = number; } public void run() { System.out.println("Thread" + this.number); } } } Thread Callable Future package threads; 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; /** * Java Callable Future Sample * https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/Callable.html * @author padaboo IB Aleksandrov */ class CallableFutureSample { public static void main(String[] args) throws ExecutionException, InterruptedException{ CallableFutureSample app = new CallableFutureSample(); app.callableTest(); } private void callableTest() throws ExecutionException, InterruptedException{ ExecutorService ex = Executors.newCachedThreadPool(); CallableThread call = new CallableThread(); Future<Integer> future = ex.submit(call); System.out.println(future.get()); ex.shutdown(); } class CallableThread implements Callable<Integer>{ public Integer call() throws Exception { int i = 1; return i; } } } Thread Count Down Latch package threads; import java.util.concurrent.CountDownLatch; /** *https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/CountDownLatch.html * @author padaboo IB Aleksandrov */ public class CountDownLatchSample { public static void main(String args[]) throws InterruptedException { CountDownLatchSample app = new CountDownLatchSample(); app.CountDownLatchTest(); } private void CountDownLatchTest() throws InterruptedException{ CountDownLatch startSignal = new CountDownLatch(1); CountDownLatch doneSignal = new CountDownLatch(2); for (int i = 0; i < 2; ++i) // create and start threads new Thread(new Worker(startSignal, doneSignal)).start(); startSignal.countDown(); // let all threads proceed doneSignal.await(); } class Worker implements Runnable { private final CountDownLatch startSignal; private final CountDownLatch doneSignal; private Worker(CountDownLatch startSignal, CountDownLatch doneSignal) { this.startSignal = startSignal; this.doneSignal = doneSignal; } public void run() { try { startSignal.await(); doWork(); doneSignal.countDown(); } catch (InterruptedException ex) {} // return; } void doWork() { System.out.println("Work"); } } } Scheduled Thread Pool package threads; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; /** * https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ScheduledExecutorService.html * @author Padaboo IB Aleksandrov */ public class ScheduledThreadPoolSample { public static void main(String[] args) throws InterruptedException { ScheduledThreadPoolSample app = new ScheduledThreadPoolSample(); } private void ScheduledTest() throws InterruptedException{ ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(5); for(int i=0; i<3; i++){ Thread.sleep(1000); WorkerThread worker = new WorkerThread("Run"); scheduledThreadPool.schedule(worker, 10, TimeUnit.SECONDS); } //add some delay to let some threads spawn by scheduler Thread.sleep(30000); scheduledThreadPool.shutdown(); while(!scheduledThreadPool.isTerminated()){ //wait for all tasks to finish } System.out.println("Finished all threads"); } public class WorkerThread implements Runnable{ private String command; public WorkerThread(String str){ this.command = str; } @Override public void run() { processCommand(); } private void processCommand() { try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } } @Override public String toString(){ return this.command; } } } Thread synchronized package threads; /** * Java syncronized * @author Padaboo IB Aleksandrov */ public class ThreadSyncSample{ Sync synchObj; public static void main(String[] args){ ThreadSyncSample app = new ThreadSyncSample(); app.syncTest(); } private void syncTest(){ synchObj = new Sync(); Runnable r = new Runnable() { public void run() { //synchronized method synchObj.plus(); System.out.println("synchronized method" + synchObj.getJ()); } }; Thread t = new Thread(r); t.start(); } class Sync{ int j = 1; public synchronized void plus(){ j++; } public synchronized int getJ(){ return j; } public void syncTest(){ synchronized (this) { System.out.println("notifyAll"); this.notifyAll(); } } } } Net Client socket package net; import java.io.BufferedReader; import java.io.InputStreamReader; import java.net.Socket; /** * https://docs.oracle.com/javase/tutorial/networking/sockets/readingWriting.html * @author Padaboo IB Aleksandrov */ public class ClientSocketSample { public static void main(String[] args) throws Exception { Socket s = new Socket("127.0.0.1", 8080); BufferedReader input = new BufferedReader(new InputStreamReader(s.getInputStream())); String answer = input.readLine(); System.out.println(answer); System.exit(0); } } Server socket package net; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; import java.util.Date; /** * https://docs.oracle.com/javase/tutorial/networking/sockets/clientServer.html * @author padaboo IB Aleksandrov */ public class ServerSocketSample { public static void main(String[] args) throws Exception { ServerSocket listener = new ServerSocket(8080); try { while (true) { Socket socket = listener.accept(); try { PrintWriter out = new PrintWriter(socket.getOutputStream(), true); out.println(new Date().toString()); } finally { socket.close(); } } } finally { listener.close(); } } } Thread server package net; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; import java.util.Scanner; import java.util.logging.Level; import java.util.logging.Logger; /** * Thread Server messages * @author Padaboo IB Aleksandrov */ public class ThreadServerSample { public static void main(String[] args){ ThreadServerSample app = new ThreadServerSample(); try { app.startUp(); } catch (IOException ex) { Logger.getLogger(ThreadServerSample.class.getName()).log(Level.SEVERE, null, ex); } } private void startUp() throws IOException{ ServerSocket sock = new ServerSocket(8080); int i = 1; while(true){ Socket in = sock.accept(); Runnable r = new ThreadServer(in); Thread t = new Thread(r); t.start(); } } class ThreadServer implements Runnable{ Socket in; private ThreadServer(Socket in) { this.in = in; } public void run() { try { InputStream inStream = in.getInputStream(); OutputStream outStream = in.getOutputStream(); Scanner in = new Scanner(inStream); PrintWriter out = new PrintWriter(outStream); while(in.hasNextLine()){ String line = in.nextLine(); out.println(line); } } catch (IOException ex) { Logger.getLogger(ThreadServerSample.class.getName()).log(Level.SEVERE, null, ex); } } } } Url sample package net; import java.io.BufferedReader; import java.io.InputStreamReader; import java.net.URL; /** * https://docs.oracle.com/javase/tutorial/networking/urls/readingURL.html * @author padaboo IB Aleksandrov */ public class UrlSample { public static void main(String[] args) throws Exception { URL oracle = new URL("http://192.168.0.101/"); BufferedReader in = new BufferedReader( new InputStreamReader(oracle.openStream())); String inputLine; while ((inputLine = in.readLine()) != null) System.out.println(inputLine); in.close(); } } Mysql jdbc package jdbcmysql; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.Statement; /** * jdbc mysql example (have a dump file) * Connector http://dev.mysql.com/downloads/connector/j/ * Statement https://docs.oracle.com/javase/tutorial/jdbc/basics/processingsqlstatements.html * Prepared http://docs.oracle.com/javase/tutorial/jdbc/basics/prepared.html * @author Padaboo IB Aleksandrov */ public class MysqlConnectSample { public static void main(String[] args) throws Exception { Connection conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/jdbctest","root", ""); String query = "SELECT * FROM jdbctest.Users;"; //execute mysql procedure //CallableStatement stmt; Statement stmt = conn.createStatement(); ResultSet rs = stmt.executeQuery(query); //stmt.executeUpdate(sql); ResultSetMetaData md = rs.getMetaData(); System.out.println("count " + md.getColumnCount()); while (rs.next()) { int id = rs.getInt("id"); System.out.println(id); } rs.close(); } } Dump CREATE DATABASE `jdbctest` CHARACTER SET utf8 COLLATE utf8_general_ci; CREATE TABLE `jdbctest`.`Users` ( `id` INT NOT NULL AUTO_INCREMENT, `name` VARCHAR(128) NULL, `session_key` VARCHAR(128) NULL, `email` VARCHAR(128) CHARACTER SET 'utf8' COLLATE 'utf8_general_ci' NULL, `password` VARCHAR(128) NULL, `activation_key` VARCHAR(128) CHARACTER SET 'utf8' COLLATE 'utf8_general_ci' NULL, PRIMARY KEY (`id`)); INSERT INTO `jdbctest`.`Users` (`name`, `session_key`, `email`, `password`, `activation_key`) VALUES ('ivan2', 'asdasddd', 'jetananas@yandex.ru', 'asdasad', 'asaadads'); INSERT INTO `jdbctest`.`Users` (`name`, `session_key`, `email`, `password`, `activation_key`) VALUES ('ivan1', 'asdasddd', 'jetananas@yandex.ru', 'asdasad', 'asaadads');