Tutorial by Examples: er

Border layout

import static java.awt.BorderLayout.*; import javax.swing.*; import java.awt.BorderLayout; JPanel root = new JPanel(new BorderLayout()); root.add(new JButton("East"), EAST); root.add(new JButton("West"), WEST); root.add(new JButton("North"), NORTH); root.add(...

swing • Layout management

Avoiding NullReferenceExceptions

var person = new Person { Address = null; }; var city = person.Address.City; //throws a NullReferenceException var nullableCity = person.Address?.City; //returns the value of null This effect can be chained together: var person = new Person { Address = new Address { ...

C# Language • Null-conditional Operators

Read the entire input as a String using Scanner

You can use Scanner to read all of the text in the input as a String, by using \Z (entire input) as the delimiter. For example, this can be used to read all text in a text file in one line: String content = new Scanner(new File("filename")).useDelimiter("\\Z").next(); System.o...

Java Language • Scanner

Using custom delimiters

You can use custom delimiters (regular expressions) with Scanner, with .useDelimiter(","), to determine how the input is read. This works similarly to String.split(...). For example, you can use Scanner to read from a list of comma separated values in a String: Scanner scanner = null; tr...

Java Language • Scanner

Avoiding N*2 iteration

This is placed in a Windows Forms event handler var nameList = new BindingList<string>(); ComboBox1.DataSource = nameList; for(long i = 0; i < 10000; i++ ) { nameList.AddRange(new [] {"Alice", "Bob", "Carol" }); } This takes a long time to execute,...

C# Language • BindingList

Usefulness of interfaces

Interfaces can be extremely helpful in many cases. For example, say you had a list of animals and you wanted to loop through the list, each printing the sound they make. {cat, dog, bird} One way to do this would be to use interfaces. This would allow for the same method to be called on all of th...

Java Language • Interfaces

Deserialization using System.Web.Script.Serialization.JavaScriptSerializer

The JavaScriptSerializer.Deserialize<T>(input) method attempts to deserialize a string of valid JSON into an object of the specified type <T>, using the default mappings natively supported by JavaScriptSerializer. using System.Collections; using System.Web.Script.Serialization; // ....

.NET Framework • JSON Serialization

Deserialization using Json.NET

internal class Sequence{ public string Name; public List<int> Numbers; } // ... string rawJSON = "{\"Name\":\"Fibonacci Sequence\",\"Numbers\":[0, 1, 1, 2, 3, 5, 8, 13]}"; Sequence sequence = JsonConvert.DeserializeObject<Seque...

.NET Framework • JSON Serialization

Run code only if there is a value present

Optional<String> optionalWithValue = Optional.of("foo"); optionalWithValue.ifPresent(System.out::println);//Prints "foo". Optional<String> emptyOptional = Optional.empty(); emptyOptional.ifPresent(System.out::println);//Does nothing.

Java Language • Optional

HTML output from web server

PHP can be used to add content to HTML files. While HTML is processed directly by a web browser, PHP scripts are executed by a web server and the resulting HTML is sent to the browser. The following HTML markup contains a PHP statement that will add Hello World! to the output: <!DOCTYPE html&gt...

PHP • Getting started with PHP

Using GET and no parameters

var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function () { if (xhttp.readyState === XMLHttpRequest.DONE && xhttp.status === 200) { //parse the response in xhttp.responseText; } }; xhttp.open("GET", "ajax_info.txt", true); xhttp.send(...

JavaScript • AJAX

Difference between Object.key and Object.prototype.key

Unlike in languages like Python, static properties of the constructor function are not inherited to instances. Instances only inherit from their prototype, which inherits from the parent type's prototype. Static properties are never inherited. function Foo() {}; Foo.style = 'bold'; var foo = ne...

JavaScript • Inheritance

Generator Expressions

Generator expressions are very similar to list comprehensions. The main difference is that it does not create a full set of results at once; it creates a generator object which can then be iterated over. For instance, see the difference in the following code: # list comprehension [x**2 for x in r...

Python Language • List comprehensions

Basic use of map, itertools.imap and future_builtins.map

The map function is the simplest one among Python built-ins used for functional programming. map() applies a specified function to each element in an iterable: names = ['Fred', 'Wilma', 'Barney'] Python 3.x3.0 map(len, names) # map in Python 3.x is a class; its instances are iterable # Out: &...

Python Language • Map Function

Basic use of filter

To filter discards elements of a sequence based on some criteria: names = ['Fred', 'Wilma', 'Barney'] def long_name(name): return len(name) > 5 Python 2.x2.0 filter(long_name, names) # Out: ['Barney'] [name for name in names if len(name) > 5] # equivalent list comprehension #...

Python Language • Filter

Non-HTML output from web server

In some cases, when working with a web server, overriding the web server's default content type may be required. There may be cases where you need to send data as plain text, JSON, or XML, for example. The header() function can send a raw HTTP header. You can add the Content-Type header to notify t...

PHP • Getting started with PHP

Remainder / Modulus (%)

The remainder / modulus operator (%) returns the remainder after (integer) division. console.log( 42 % 10); // 2 console.log( 42 % -10); // 2 console.log(-42 % 10); // -2 console.log(-42 % -10); // -2 console.log(-40 % 10); // -0 console.log( 40 % 10); // 0 This operator returns th...

JavaScript • Arithmetic (Math)

The Increment/Decrement Operators (++/--)

Variables can be incremented or decremented by 1 using the ++ and -- operators, respectively. When the ++ and -- operators follow variables, they are called post-increment and post-decrement respectively. int a = 10; a++; // a now equals 11 a--; // a now equals 10 again When the ++ and -- ope...

Java Language • Operators

Logic Operators with Booleans

var x = true, y = false; AND This operator will return true if both of the expressions evaluate to true. This boolean operator will employ short-circuiting and will not evaluate y if x evaluates to false. x && y; This will return false, because y is false. OR This operator wil...

JavaScript • Comparison Operations

Relational operators (<, <=, >, >=)

When both operands are numeric, they are compared normally: 1 < 2 // true 2 <= 2 // true 3 >= 5 // false true < false // false (implicitly converted to numbers, 1 > 0) When both operands are strings, they are compared lexicographically (according to alphabeti...

JavaScript • Comparison Operations