jdk1.8 lambda表达式处理集合的一些用法

package com.kerry;

import java.time.Clock;
import java.time.Duration;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.Month;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.List;
import java.util.Map;
import java.util.OptionalInt;
import java.util.TimeZone;
import java.util.stream.Collectors;


public class JDK8Test {

	public static void streamTest(){
		
		List tasks =Arrays.asList(new Task("OPEN", 3),new Task("PENDING", 6),
				new Task("PENDING", 6),new Task("CLOSE", 10),new Task("OPEN", 5));
		
		
		//循环
		tasks.forEach(task -> {
			//处理逻辑.....
			if (task.getStatus().equals("OPEN")) {
//				.task....
			}
		});
		
		
		tasks.forEach(System.out::println);
		
		//过滤list
		List filterTasks = tasks.stream()
				.filter(t -> t.getStatus() == "OPEN" && t.getScore()==3)
				.collect(Collectors.toList());
		
		
		
		
		
		//获取集合最大最小值
		OptionalInt max = tasks.stream()
	    .filter( task -> task.getStatus() == "OPEN" )//过滤条件
	    .mapToInt(Task::getScore)
	    .max();//获取open状态最大的值
//		.min();//获取open状态最小的值
		
		
		//求和
		int totalOpenScore  = tasks.stream()
			    .filter( task -> task.getStatus() == "OPEN" )//过滤条件
			    .mapToInt(task -> task.getScore()) // Task::getScore
	    		.sum(); //获取open状态的值求和
		
		//并行计算求和
		int totalScore = tasks.stream()
		.parallel()
		.map(task -> task.getScore())
		.reduce(0, Integer::sum);
		
		//分组统计
		Map> map = tasks.stream().
				collect(Collectors.groupingBy(Task::getStatus));
		
		
		//求百分比
		Collection result = 
				tasks.stream()
			.mapToInt(Task::getScore)
			.asLongStream()
			.mapToDouble(score -> (float)score / totalScore)
			.boxed()
			.mapToLong(weight -> (long)(weight*100))
			.mapToObj(percent ->percent+"%")
			.collect(Collectors.toList());
		
		
		System.out.println("各百分比："+result);
		System.out.println("分组统计:"+map);
		System.out.println("过滤求和："+totalOpenScore);
		System.out.println("最大值："+max.getAsInt());
		System.out.println("总计："+totalScore);
	}

	public static void main(String args[]) {
		streamTest();
		
		
		Clock c = Clock.systemDefaultZone();
		System.out.println(c.instant());
		System.out.println(c.millis());
		LocalDateTime ldt = LocalDateTime.now();
		System.out.println(ldt);
		System.out.println(LocalTime.now());
		System.out.println(LocalDate.now());
		
		
		// Get duration between two dates
		final LocalDateTime from = LocalDateTime.of( 2014, Month.APRIL, 16, 0, 0, 0 );
		final LocalDateTime to = LocalDateTime.of( 2015, Month.APRIL, 16, 0, 0, 0 );
		 
		final Duration duration = Duration.between( from, to );
		System.out.println( "Duration in days: " + duration.toDays() );
		System.out.println( "Duration in hours: " + duration.toHours() );
		
		
	}
}

package com.kerry;


public class Task {


private String status;
private Integer score;

public Task(String status, Integer score) {
this.status = status;
this.score = score;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public Integer getScore() {
return score;
}
public void setScore(Integer score) {
this.score = score;
}
@Override
public String toString() {
return "Task [status=" + status + ", score=" + score + "]";
}

}