jdk8 lambda 常用流操作

/**
 * 
 */
package com.lambdasTest.stream;

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.function.BinaryOperator;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * jdk8 lambda 函数式编程之stream
 * 
 * @Date Oct 23, 2017 12:27:17 PM
 */
public class StreamOfLambdas {
    public static void main(String[] agrs) {
        // collect(toList())
        List collected = Stream.of("a", "b", "c", "d").collect(Collectors.toList());
        System.out.println(collected); // [a, b, c, d]
        System.out.println(Arrays.asList("a", "b", "c", "d"));      //[a, b, c, d]

        // map 将一个流中的值转换成一个新的流
        collected = Stream.of("a", "b", "hEllo").map(string -> string.toUpperCase()).collect(Collectors.toList());
        System.out.println(collected); // [A,B,HELLO]

        // filter
        List beginningWithNumbers = Stream.of("a", "1abc", "5acs").filter(value -> isDigit(value.charAt(0))).collect(Collectors.toList());
        System.out.println("filter: " + beginningWithNumbers); // [1abc, 5acs]

        // flatmap 可用Stream替换值，然后将多个Stream连接成一个Stream
        List together = Stream.of(Arrays.asList(1, 2), Arrays.asList(3, 4)).flatMap(numbers -> numbers.stream()).collect(Collectors.toList());
        System.out.println(together); // [1, 2, 3, 4]

        // min and max
        List tracks = Arrays.asList(new Track("bakai", 524), new Track("Vlolets for your furs", 373), new Track("Time was", 451));
        Track shortestTrack = tracks.stream().min(Comparator.comparing(track->track.getLength())).get();
        System.out.println(shortestTrack.getName().toString() + shortestTrack.getLength()); // Vlolets for your furs373

        // reduce 从一组值中生成一个值
        int count = Stream.of(1, 2, 3).reduce(0, (acc, element) -> acc + element);
        System.out.println(count);      //6

        BinaryOperator accumulator = (acc, element) -> acc + element;
        count = accumulator.apply(accumulator.apply(accumulator.apply(0, 1), 2), 3);
        System.out.println(count);  //6
    }

    public static boolean isDigit(char c) {
        return (int) c >= 48 && (int) c <= 57;
    }

}

class Track {
    private String name;
    private int length;

    /**
     * @param name
     *            曲目
     * @param length
     *            长度
     */
    public Track(final String name, final int length) {
        super();
        this.name = name;
        this.length = length;
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name
     *            the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the length
     */
    public int getLength() {
        return length;
    }

    /**
     * @param length
     *            the length to set
     */
    public void setLength(int length) {
        this.length = length;
    }

}