Java 偶基數判斷

一般的比較法

int a = 3;
int b = 4;
 
System.out.println(a%2==0?"a是偶數":"a是奇數");
System.out.println(b%2==0?"b是偶數":"b是奇數");

較快速的比較法

int a = 3;
int b = 4;
 
System.out.println((a&1)==0?"a是偶數":"a是奇數");
System.out.println((b&1)==0?"b是偶數":"b是奇數");

3 & 1 = 0011 & 0001 = 1
4 & 1 = 0100 & 0001 = 0

用%的話就顯得比&還要慢了

來源

Java 費氏數列

import java.util.Scanner;

public class Fibonacci {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        System.out.println("輸入數列大小: ");
        int a = sc.nextInt();
        long [] fin = new long[a];
        fin[0] = 1;
        fin[1] = 1;
  
        for(int i = 2; i < a; i++){
             fin[i] = (fin[i-1] + fin[i-2]);
        }
  
        for(long b : fin ){
             System.out.print(b + " ");
        }
  
    }
}

查詢本機IP

import java.net.*;

public class LookIP {
   public static void main(String[] args){
      try{
         InetAddress host = InetAddress.getLocalHost();
         System.out.println("網域名稱: " + host.getHostName());
         System.out.println("IP位址: " + host.getHostAddress());
      }catch(Exception e){
         e.printStackTrace();
      }
   }
}