java 大数据量使用List，Map存取速度的比较
package com.zl.mybatis.plus;
import java.util.*;
public class Main {
public static void main(String arg[]) {
Map<Integer, User> userMap = new HashMap<>();
List<User> list = new ArrayList<>();
for (int i = 0; i < 1000000; i++) {
User user=new User();
user.setName("name" + i);
user.setSex("女");
user.setMath(60);
user.setChinese(120);
user.setEnglish(60);
userMap.put(i, user);
list.add(user);
}
Long el = System.currentTimeMillis();
for (User user : list) {
int math = user.getMath();
int chinese = user.getChinese();
int english = user.getEnglish();
int sum = math + chinese + english;
}
Long ej = System.currentTimeMillis();
System.out.println("list for-each时间差：" + (ej - el));
System.out.println("**********************************************");
Long e = System.currentTimeMillis();
int size=list.size();
for (int i=0;i<size;i++){
User user=list.get(i);
int math = user.getMath();
int chinese = user.getChinese();
int english = user.getEnglish();
int sum = math + chinese + english;
}
Long le = System.currentTimeMillis();
System.out.println("list时间差：" + (le - e));
System.out.println("**********************************************");
Long l = System.currentTimeMillis();
for (Map.Entry<Integer,User> entry : userMap.entrySet()) {
User user=entry.getValue();
int math = user.getMath();
int chinese = user.getChinese();
int english = user.getEnglish();
int sum = math + chinese + english;
}
Long ll = System.currentTimeMillis();
System.out.println("map时间差：" + (ll - l));
}
}