背景:
公众号上偶尔看到一道阿里编程面试题,简单答一下哦 ~
直接上代码:
package test;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.util.*;
/**
* @Author: yuanj
* @CreateDate: 2018/6/27 21:33
* @Version: 1.0
*/
public class LogKeywords {
public static void main(String[] args) throws Exception{
File file = new File("src/main/java/test/sys_info.log");
System.out.println("请输入关键字:(以空格为间隔)");
Scanner scanner = new Scanner(System.in);
String input = scanner.nextLine();
String[] keywords = input.split(" ");
long start = System.currentTimeMillis();
BufferedReader bufferedReader = new BufferedReader(new FileReader(file));
System.out.println(Arrays.toString(keywords));
//该map的key为关键字,value为关键字出现次数
Map<String, Integer> map = new HashMap<String, Integer>();
String result = null;
//按行读取日志文件,对每一行分别计算关键字次数,累加进map
while((result = bufferedReader.readLine()) != null){
for(int i = 0; i < keywords.length; i++ ){
//通过split方法实现搜索关键字次数功能
int count = (result.split(keywords[i])).length - 1;
map.put(keywords[i], (map.get(keywords[i]) == null ? 0 : map.get(keywords[i])) + count);
}
}
//将上面map的每个Entry存入list
ArrayList<Map.Entry<String, Integer>> entryArrayList = new ArrayList<Map.Entry<String, Integer>>();
for (Map.Entry<String, Integer> m : map.entrySet()){
entryArrayList.add(m);
}
//自定义list的比较器,根据value从大到小排列Entry元素
Collections.sort(entryArrayList, new Comparator<Map.Entry<String, Integer>>() {
public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
return o2.getValue() - o1.getValue();
}
});
for (Map.Entry<String, Integer> m : entryArrayList){
System.out.println(m.getKey() + ":" + m.getValue());
}
long end = System.currentTimeMillis();
System.out.println("搜索耗时:" + (end - start) + " ms");
}
}
测试:
首先测试日志文件大小为 160M:
测试结果: