问答题
1.怎样实例化一个Calendar对象?
Calendar ca=Calendar.getInstance();
2.Calendar对象调用set(1949,9,1)设置的年月日分别是多少?
就是1949,9,1
3.怎样得到一个1—100的随机数?
int a=(int) (Math.random()*100+1); //或者 Random ra=new Random(); int b=ra.nextInt(100)+1;
4.有集合{1,2,3,4}和集合{1,3,7,9,11}编写一个应用程序输出交集并集差集
Set<Integer> s1=new HashSet<>(); s1.add(1); s1.add(2); s1.add(3); s1.add(4); Set<Integer> s2=new HashSet<>(); s2.add(1); s2.add(3); s2.add(7); s2.add(9); s2.add(11); s1.retainAll(s2);//交集 System.out.println(s1); s1.addAll(s2);//并集 System.out.println(s1); s1.removeAll(s2);//差集 System.out.println(s1);
5.硬盘中有2个重要的属性:价格和容量,编写一个应用程序,使用TreeMap<K,V>类,分别按照价格和容量排序输出10个硬盘的信息
package cn.littlepage.game; import java.util.TreeMap; public class test { public static void main(String[] args) { Disk d1=new Disk(300, 500); Disk d2=new Disk(200, 200); Disk d3=new Disk(800, 300); Disk d4=new Disk(600, 800); Key kp1=new Key(d1.price); Key kp2=new Key(d2.price); Key kp3=new Key(d3.price); Key kp4=new Key(d4.price); Key kc1=new Key(d1.capacity); Key kc2=new Key(d2.capacity); Key kc3=new Key(d3.capacity); Key kc4=new Key(d4.capacity); TreeMap<Key, Disk> diskMap=new TreeMap<>(); diskMap.put(kp1, d1); diskMap.put(kp2, d2); diskMap.put(kp3, d3); diskMap.put(kp4, d4); TreeMap<Key, Disk> diskMap2=new TreeMap<>(); diskMap2.put(kc1, d1); diskMap2.put(kc2, d2); diskMap2.put(kc3, d3); diskMap2.put(kc4, d4); System.out.println(diskMap); System.out.println(diskMap2); } } class Disk{ public int price; public int capacity; public Disk(int price, int capacity) { super(); this.price = price; this.capacity = capacity; } @Override public String toString() { return "Disk [price=" + price + "元, capacity=" + capacity + "GB]\n"; } } class Key implements Comparable{ public int num=0; public Key(int num) { super(); this.num = num; } @Override public int compareTo(Object o) { Key k=(Key)o; return num-k.num; } }
控制台:{[email protected]=Disk [price=200元, capacity=200GB] , [email protected]=Disk [price=300元, capacity=500GB] , [email protected]=Disk [price=600元, capacity=800GB] , [email protected]=Disk [price=800元, capacity=300GB] } {[email protected]=Disk [price=200元, capacity=200GB] , [email protected]=Disk [price=800元, capacity=300GB] , [email protected]=Disk [price=300元, capacity=500GB] , [email protected]=Disk [price=600元, capacity=800GB] }
原文地址:https://www.cnblogs.com/littlepage/p/9902882.html
时间: 2024-10-14 11:39:30