EffectiveJava阅读笔记（一）

整型处理

IntStream

求1-100中的偶数之和

        int result = IntStream.rangeClosed(1, 100)
                .filter(a -> a % 2 == 0)
                .sum();
        System.out.println(result);

int[] 与 Integer[] 转换

        int[] intArray = {1,2,3,4,5};
        Integer[] integers = Arrays.stream(intArray)
                //each boxed to an {@code Integer}.
                // 将每个int转成Integer
                .boxed()
                .toArray(Integer[]::new);
        System.out.println(Arrays.toString(integers));

字符串处理

join方法

        String[] str = {"hello", "world", "fonxian"};
        String s = String.join(",", str);
        System.out.println(s);

集合处理

去掉List中的重复元素

List<String> words = Arrays.asList("a", "b", "c", "d", "a", "b");
        words.stream()
                .distinct()
                .collect(Collectors.toList())
                .forEach(System.out::println);

接口

默认实现

interface Animal{

    void move();

    // 默认实现
    default void eat(){
        System.out.println("eat");
    }
}

class Dog implements Animal{

    @Override
    public void move() {

    }
}

class Cat implements Animal{

    @Override
    public void move() {

    }