Java常用语法

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.TreeMap;
import java.util.TreeSet;

public class Main {
    
    public static void main(String[] args) throws IOException {
        //输入输出流
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter log = new BufferedWriter(new OutputStreamWriter(System.out));
        log.flush();
        //HashMap 赋值，查询
        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
        int val = 0;
        map.put(val, map.getOrDefault(val, 0) + 1);
        for(Map.Entry<Integer, Integer> entry : map.entrySet())
        {
            int a = entry.getKey(); 
            int b = entry.getValue();
        }
        //TreeMap
        TreeMap<Integer, Integer> map2 = new TreeMap<Integer, Integer>();
        //HashSet 
        HashSet<Integer> set1 = new HashSet<Integer>();
        //TreeSet
        TreeSet<Integer> set2 = new TreeSet<Integer>();
        int e = 1;
        Integer l = set2.floor(e);//窗口中小于等于e的最大值，找不到返回null
        Integer r = set2.ceiling(e);//窗口中大于等于e的最小值，找不到返回null
        set2.remove(e);//具体移除某个值
        
        //排序
        int[] a = new int[18];
        Integer[] b = new Integer[18];
        int l = 2, r = 3;
        //从小到大
        Arrays.sort(a, l, r + 1);
        //从大到小
        Arrays.sort(b, l, r + 1, (x, y) -> {return y - x;});
        
        //链表
        List<Integer> ans = new ArrayList<Integer>();
        //队列
        Queue<Integer> q1 = new LinkedList<Integer>();
        //双端队列
        Deque<Integer> q2 = new LinkedList<Integer>();
        //数组队列
        ArrayList<Integer>[] head = new ArrayList[10];
        for(int i = 0;i < 10;i ++) head[i] = new ArrayList<Integer>();
        //优先队列
        //小根堆
        PriorityQueue<Integer> q3 = new PriorityQueue<Integer>();
        //大根堆
        PriorityQueue<Integer> q4 = new PriorityQueue<Integer>((x, y) -> {return y - x;});
    
    } 
}
class Edge implements Comparable<Edge>
{
    int a, b, c;
    Edge(int a, int b, int c)
    {
        this.a = a;
        this.b = b;
        this.c = c;
    }
    @Override
    public int compareTo(Edge o) {
        // TODO 自动生成的方法存根
        return Integer.compare(c, o.c);
    }
    
}