Java 8 新特性

Java 8 Features:

• Lambda expression
• Stream API
• Functional interface
• Default and static methods
• Optional class
• Nashorn – JavaScript runtime engine
• Annotation on Java Types
• Unsigned Integer Arithmetic
• Repeating annotations
• New Date and Time API

Unsigned Integer Arithmetic

answer from stackoverflow

Well, even in Java 8, long and int are still signed, only some methods treat them as if they were unsigned. If you want to write unsigned long literal like that, you can do

static long values = Long.parseUnsignedLong("18446744073709551615");

public static void main(String[] args) {
    System.out.println(values); // -1
    System.out.println(Long.toUnsignedString(values)); // 18446744073709551615
}

Stream API

pass

Lambda表达式和函数式接口

方法引用

更好的类型推断

pass

Date/Time API(JSR 310)

pass

Optional

pass

接口的默认方法和静态方法

pass

Java编译器 参数名称

Nashorn JavaScript引擎

Nashorn has been included with Java 8 through JDK 14

嗯是的，Jdk 15 就没有了。

Nashorn development continues on GitHub as a standalone OpenJDK project and the separate release can be used in Java project from Java 11 and up.

Base64 API

拓宽注解的应用场景

重复注解

Annotation on Java Types

import java.lang.annotation.*;
@Target(ElementType.TYPE_USE)
@interface TypeAnnoDemo {
}

public class MyClass {
    public static void main(String[] args) {
        @TypeAnnoDemo
        String s = "Hello,I am annotated with a type annotation";
        System.out.println(s);
        myMethod();
    }

    static @TypeAnnoDemo int myMethod() {
        System.out.println("There is a use of annotation with the return type of the function");
        return 0;
    }
}