Java-8 Features

interface Formula {
    double calculate(int a);

    default double sqrt(int a) {
        return Math.sqrt(a);
    }
}

Formula formula = new Formula() {
    @Override
    public double calculate(int a) {
        return sqrt(a * 100);
    }
};

formula.calculate(100);     // 100.0
formula.sqrt(16);



List names = Arrays.asList("peter", "anna", "mike", "xenia");

Collections.sort(names, new Comparator() {
    @Override
    public int compare(String a, String b) {
        return b.compareTo(a);
    }
});

Collections.sort(names, (String a, String b) -> {
    return b.compareTo(a);
});

Collections.sort(names, (a, b) -> b.compareTo(a));



@FunctionalInterface
interface Converter {
    T convert(F from);
}
Converter converter = (from) -> Integer.valueOf(from);
Integer converted = converter.convert("123");
System.out.println(converted);    // 123


Converter converter = Integer::valueOf;
Integer converted = converter.convert("123");
System.out.println(converted);   // 123

class Something {
    String startsWith(String s) {
        return String.valueOf(s.charAt(0));
    }
}

Something something = new Something();
Converter converter = something::startsWith;
String converted = converter.convert("Java");
System.out.println(converted);    // "J"

class Person {
    String firstName;
    String lastName;

    Person() {}

    Person(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }
}

interface PersonFactory

{

    P create(String firstName, String lastName);
}

PersonFactory personFactory = Person::new;
Person person = personFactory.create("Peter", "Parker")

http://winterbe.com/posts/2014/03/16/java-8-tutorial/