Java 8: The Next Level of Java Programming
Lambda Expressions
One of the most significant new features of Java 8 is lambda expressions. Lambda expressions are a concise way to represent anonymous functions, which can be passed as arguments to methods or stored as variables. This can make your code much more expressive and concise, especially when working with collections.
List<String> names = Arrays.asList("John", "Jane", "Jack");
names.forEach(name -> System.out.println(name));
In this example, we use a lambda expression to iterate over the names in the list and print them to the console.
Functional Interfaces
Lambda expressions are based on functional interfaces, which are interfaces that have exactly one abstract method. Java 8 introduces several new functional interfaces in the java.util.function package, such as Predicate, Consumer, and Supplier. These interfaces can be used with lambda expressions to perform operations on collections.
Predicate<String> startsWithJ = (String name) -> name.startsWith("J");
List<String> names = Arrays.asList("John", "Jane", "Jack");
names.stream().filter(startsWithJ).forEach(System.out::println);
In this example, we use a Predicate functional interface to filter the names that start with "J" from the list and print them to the console.
Streams
Another major feature of Java 8 is streams, which are a new way of processing collections. Streams are a sequence of elements that can be processed in parallel or sequentially. They allow you to perform operations on collections in a declarative way, making your code more concise and readable.
List<String> names = Arrays.asList("John", "Jane", "Jack");
long count = names.stream().filter(name -> name.startsWith("J")).count();
System.out.println(count);
In this example, we use a stream to filter the names that start with "J" from the list and count them.
Date and Time API
Java 8 also introduces a new Date and Time API that replaces the old java.util.Date and java.util.Calendar classes. The new API provides a more intuitive way to work with dates and times, and it is also thread-safe and immutable.
LocalDate date = LocalDate.now();
System.out.println(date);
In this example, we use the LocalDate class to get the current date and print it to the console.
Optional Class
The Optional class is another new feature of Java 8 that provides a way to represent null values in a more meaningful way. The Optional class can be used to prevent NullPointerExceptions and make your code more robust.
Optional optional = Optional.ofNullable(null);
System.out.println(optional.orElse("Default Value"));
In this example, we use the Optional class to provide a default value when the value is null.
Default Methods
Java 8 also introduces default methods in interfaces, which allow you to provide a default implementation for a method in an interface. This can be useful when you want to add a new method to an existing interface without breaking existing implementations.
interface MyInterface {
default void myMethod() {
System.out.println("Default implementation");
}
}
class MyClass implements MyInterface {
}
MyClass obj = new MyClass();
obj.myMethod(); // Output: Default implementation
In this example, we define a default implementation for the myMethod() method in the MyInterface interface, and then we create a MyClass object and call the myMethod() method on it.
Method References
Method references are a shorthand syntax for lambda expressions. They allow you to refer to an existing method by name instead of defining a new lambda expression. This can make your code more readable and concise.
List names = Arrays.asList("John", "Jane", "Jack");
names.forEach(System.out::println);
In this example, we use a method reference to print the names in the list to the console.
Parallel Array Sorting
Java 8 also introduces a new parallel sorting algorithm for arrays. This can significantly improve the performance of sorting large arrays on multi-core machines.
int[] numbers = {5, 3, 1, 6, 8, 4, 2, 7};
Arrays.parallelSort(numbers);
System.out.println(Arrays.toString(numbers));
In this example, we use the parallelSort() method of the Arrays class to sort an array of integers in parallel.
Nashorn JavaScript Engine
Java 8 includes a new JavaScript engine called Nashorn, which is faster and more efficient than the previous Rhino engine. Nashorn also provides better interoperability with Java, allowing you to call Java code from JavaScript and vice versa.
ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("JavaScript");
engine.eval("print('Hello, World!')");
In this example, we use the Nashorn JavaScript engine to print "Hello, World!" to the console.
Base64 Encoding and Decoding
Java 8 includes a new class called java.util.Base64 that provides methods for encoding and decoding data in Base64 format.
String originalInput = "test input";
String encodedString = Base64.getEncoder().encodeToString(originalInput.getBytes());
System.out.println(encodedString);
byte[] decodedBytes = Base64.getDecoder().decode(encodedString);
String decodedString = new String(decodedBytes);
System.out.println(decodedString);
In this example, we encode a string in Base64 format and then decode it back to the original string.
ConcurrentHashMap
Java 8 introduces a new method called forEach() to the ConcurrentHashMap class, which allows you to perform a specific action on each key-value pair in the map in a thread-safe manner.
ConcurrentHashMap map = new ConcurrentHashMap<>();
map.put("A", 1);
map.put("B", 2);
map.put("C", 3);
map.forEach((key, value) -> System.out.println(key + " = " + value));
In this example, we use the forEach() method to print all the key-value pairs in the ConcurrentHashMap.
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