设计日志存储系统

/*
 * Leetcode 635: Design Log Storage System
 * 
 * Solution using Java Streams:
 * 1. Use a list to store log entries as a pair of (id, timestamp).
 * 2. Use a map to define the granularity levels (year, month, day, hour, minute, second).
 * 3. For the retrieve function, use Java Streams to filter logs based on the given start and end timestamps according to the specified granularity.
 */
 
import java.util.*;
import java.util.stream.Collectors;
 
public class LogSystem {
    private List<int[]> logs;
    private Map<String, Integer> granularityMap;
    
    public LogSystem() {
        logs = new ArrayList<>();
        granularityMap = new HashMap<>();
        granularityMap.put("Year", 4);
        granularityMap.put("Month", 7);
        granularityMap.put("Day", 10);
        granularityMap.put("Hour", 13);
        granularityMap.put("Minute", 16);
        granularityMap.put("Second", 19);
    }
    
    public void put(int id, String timestamp) {
        logs.add(new int[]{id, timestamp.hashCode()});
    }
    
    public List<Integer> retrieve(String s, String e, String gra) {
        int len = granularityMap.get(gra);
        int startHash = s.substring(0, len).hashCode();
        int endHash = e.substring(0, len).hashCode();
        return logs.stream()
                    .filter(log -> log[1] >= startHash && log[1] <= endHash)
                    .map(log -> log[0])
                    .collect(Collectors.toList());
    }
}