New features about Java 8.md

New features about Java 8

Default method in interface

• 接口中可以有具体方法实现，需要加上default关键字。接口和抽象类的用法是否越来越接近，有待研究。

Lambda

• Before Java 8

	List<String> names = Arrays.asList("zhangsan","lisi","wangwu");	Collections.sort(names,new Collector<String>(){
		@Override
		public int compare(String a,String b) {
			return b.compareTo(a);
		}
	});	

• Now

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

Functional Interface

Invoke method or constructor

• invoke static method

Integer::valueOf

• invoke instance method

exampleObject::exampleMethod

• invoke constructor

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

public interface PersonFactory<P extends Person>{
	P create();
}

public class PersonTest {
	PersonFactory factory = Person::new;
	
	Person person = factory.create();
}

We can get ref of Person constructor through Person::new,and java compiler can select appropriate constructor to implement create method in PersonFactory according to method signature.

Lambda scope

Local variable in lambda