Java 8 - new important features

Java 8 has included a lot of new features, this post will explain a few important features. 

1. Lamda Expressions. 
2. Functional Interfaces. 
3. Streams
4. Nashorn

Other features. 

• Date and time api changes. 
• Foreach. 

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Lamda expressions

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Lamda expression is a function with no name and with implementation. 

A basic expression format would be..

(x, y) -> x + y

Where (x, y) are the function input parameters. And x+y is the statement executed by the function and returned. 

Example: 

FileFilter filterLamda = (File pathName) -> pathName.getName().endsWith(".png");

File dir = new File("/Users/deiveehannallazhagappan/workspace/xplore-java/supporting");

File[] files = dir.listFiles(filterLamda);

for (File f: files) {

    System.out.println("f = " + f);

}

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Functional Interfaces

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Functional interfaces are interfaces that have only one abstract method in it. 

Example: 

@FunctionalInterface

public interface TestFuncInterface {

    public void testmethod();

default void testdefaultmethod(){

         System.out.println(“default method“);

     }

}

Lamda expressions can be used to represent the instance of a functional interface. 

Note: 

• You can add default methods .

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Streams

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Streams are new feature introduced in Java 8 to simplify the logic required to process data - filtering, transforming data etc., 

For example, the below example does the following

• Creates a new array list from 1-30
• Creates a stream of integers. 
• Filters the list by extracting only no.s divisible by 3 and converts them into a integer array. 

Stream example: 

List<Integer> list = new ArrayList<Integer>();

for(int i = 1; i< 30; i++){

    list.add(i);

}

Stream<Integer> stream = list.stream();

Integer[] evenNumbersArr = stream.filter(i -> i%3 == 0).toArray(Integer[]::new);

System.out.print(evenNumbersArr);

Why streams: reduce complexity, less code. 

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Nashorn

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Nashorn is a javascript engine which allows the java applications to interact with the JS code. 

ScriptEngineManager sem = new ScriptEngineManager();

ScriptEngine engine = sem.getEngineByName("nashorn");

engine.eval("print('deiveehan')");

You can also execute an external script instead of using inline js code. 

engine.eval(new FileReader("/Users/deiveehannallazhagappan/workspace/xplore-java/supporting/js/deiveescript.js"));

You will get the output of the js code when you run the java application.