Tutorial by Examples: ti

All Javadoc comments begin with a block comment followed by an asterisk (/**) and end when the block comment does (*/). Optionally, each line can begin with arbitrary whitespace and a single asterisk; these are ignored when the documentation files are generated. /** * Fields can be documented as ...

You can get the value of other primitive data types as a String using one the String class's valueOf methods. For example: int i = 42; String string = String.valueOf(i); //string now equals "42”. This method is also overloaded for other datatypes, such as float, double, boolean, and ...

If your computation produces some return value which later is required, a simple Runnable task isn't sufficient. For such cases you can use ExecutorService.submit(Callable<T>) which returns a value after execution completes. The Service will return a Future which you can use to retrieve the r...

The ScheduledExecutorService class provides a methods for scheduling single or repeated tasks in a number of ways. The following code sample assume that pool has been declared and initialized as follows: ScheduledExecutorService pool = Executors.newScheduledThreadPool(2); In addition to the nor...

Java SE 5 It is possible to create package-level documentation in Javadocs using a file called package-info.java. This file must be formatted as below. Leading whitespace and asterisks optional, typically present in each line for formatting reason /** * Package documentation goes here; any docu...

Maps provide methods which let you access the keys, values, or key-value pairs of the map as collections. You can iterate through these collections. Given the following map for example: Map<String, Integer> repMap = new HashMap<>(); repMap.put("Jon Skeet", 927_654); repMap.p...

String str = "My String"; System.out.println(str.charAt(0)); // "M" System.out.println(str.charAt(1)); // "y" System.out.println(str.charAt(2)); // " " System.out.println(str.charAt(str.length-1)); // Last character "g" To get the nth charac...

import javax.xml.bind.annotation.XmlRootElement; @XmlRootElement public class User { private long userID; private String name; // getters and setters } By using the annotation XMLRootElement, we can mark a class as a root element of an XML file. import java.io.File; ...

Arrays are objects which provide space to store up to its size of elements of specified type. An array's size can not be modified after the array is created. int[] arr1 = new int[0]; int[] arr2 = new int[2]; int[] arr3 = new int[]{1, 2, 3, 4}; int[] arr4 = {1, 2, 3, 4, 5, 6, 7}; int len1 = ar...

A primitive data type such as int holds values directly into the variable that is using it, meanwhile a variable that was declared using Integer holds a reference to the value. According to java API: "The Integer class wraps a value of the primitive type int in an object. An object of type Int...

A short is a 16-bit signed integer. It has a minimum value of -215 (-32,768), and a maximum value of 215 ‑1 (32,767) short example = -48; short myShort = 987; short anotherShort = 17; short addedShorts = (short) (myShort + anotherShort); // 1,004 short subtractedShorts = (short) (myShort - an...

By default, long is a 64-bit signed integer (in Java 8, it can be either signed or unsigned). Signed, it can store a minimum value of -263, and a maximum value of 263 - 1, and unsigned it can store a minimum value of 0 and a maximum value of 264 - 1 long example = -42; long myLong = 284; long ano...

A boolean can store one of two values, either true or false boolean foo = true; System.out.println("foo = " + foo); // foo = true boolean bar = false; System.out.println("bar = " + bar); // bar = false boolean notFoo = !foo; System.out.prin...

Server: Start, and wait for incoming connections //Open a listening "ServerSocket" on port 1234. ServerSocket serverSocket = new ServerSocket(1234); while (true) { // Wait for a client connection. // Once a client connected, we get a "Socket" object // that c...

A byte is a 8-bit signed integer. It can store a minimum value of -27 (-128), and a maximum value of 27 - 1 (127) byte example = -36; byte myByte = 96; byte anotherByte = 7; byte addedBytes = (byte) (myByte + anotherByte); // 103 byte subtractedBytes = (byte) (myBytes - anotherByte); // 89 ...

A float is a single-precision 32-bit IEEE 754 floating point number. By default, decimals are interpreted as doubles. To create a float, simply append an f to the decimal literal. double doubleExample = 0.5; // without 'f' after digits = double float floatExample = 0.5f; // with 'f' aft...

A double is a double-precision 64-bit IEEE 754 floating point number. double example = -7162.37; double myDouble = 974.21; double anotherDouble = 658.7; double addedDoubles = myDouble + anotherDouble; // 315.51 double subtractedDoubles = myDouble - anotherDouble; // 1632.91 double scientif...

Buttons fire action events when they are activated (e.g. clicked, a keybinding for the button is pressed, ...). button.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { System.out.println("Hello World!"); } }); ...

Don't just use Optional.get() since that may throw NoSuchElementException. The Optional.orElse(T) and Optional.orElseGet(Supplier<? extends T>) methods provide a way to supply a default value in case the Optional is empty. String value = "something"; return Optional.ofNullable(v...

Use the orElseThrow() method of Optional to get the contained value or throw an exception, if it hasn't been set. This is similar to calling get(), except that it allows for arbitrary exception types. The method takes a supplier that must return the exception to be thrown. In the first example, the...