Java利用Collections實現(xiàn)獲取list集合的極值

package com.jalor;
 
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
 
public class Jalor_20180728 {
 public static void main(String[] args) {
 List<Integer> rst2 = new ArrayList<>();
 rst2.add(1);
 rst2.add(2);
 rst2.add(3);
 rst2.add(8);
 rst2.add(0);
 Collections.max(rst2);
 Collections.min(rst2);
 System.out.println("max: "+ Collections.max(rst2));
 System.out.println("min: "+ Collections.min(rst2));
 }
}

package com.cn;

import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class Test4 {
	public static void main(String[] args) {
		TotalityStandardDeviation();
	}
	
	public static void TotalityStandardDeviation(){
		List<String> list = new ArrayList<String>();
		list.add("1.24");
		list.add("2.24");
		list.add("5");
		
		String maxvalue=Collections.max(list);
		System.out.println("最大值==="+maxvalue);
		String minvalue=Collections.min(list);
		System.out.println("最小值==="+minvalue);
		int count=0;//總個數(shù)
		double sum=0;//總和
		double average=0;//平均數(shù)
		double dStdDev=0;//總體標準偏差
		
		//求總組數(shù)
		count=list.size();
		System.out.println("總個數(shù)==="+count);
		//求和
		for(int i = 0; i < list.size(); ++i)
		{
			sum += Double.parseDouble(list.get(i));
		}
		//求平均數(shù)
		average = sum/list.size();
		DecimalFormat df = new DecimalFormat(".000");
		System.out.println("總和==="+df.format(sum));
		System.out.println("平均數(shù)==="+df.format(average));
		//求總體標準偏差
		double dsum=0;
		for(int i = 0; i < list.size(); ++i)
		{
			double s=Double.parseDouble(list.get(i)) - average;
			dsum += Math.pow(s,2);
		}
		dStdDev = Math.sqrt(dsum / list.size());
		System.out.println("標準偏差值==="+df.format(dStdDev));
	}
}