Java小例子——穷举质数，求平方和，求质因子。

来源：互联网发布：中国制造业数据pmi 编辑：程序博客网时间：2024/04/24 07:14

求平方和

public static void main(String[] args) throws IOException{int n;String s;BufferedReader buf;buf=new BufferedReader(new InputStreamReader(System.in));System.out.print("请输入一个自然数：");s=buf.readLine();n=Integer.parseInt(s);System.out.print("f(n)=1");for(int i=2;i<=n;i++)System.out.print("+"+i*i);System.out.print("="+Square(n));}public static long Square(int n){long f=0;if(n<0)System.out.println("n<0，输入错误！");else if(n==1)f=1;else f=Square(n-1)+n*n;return f;}

穷举质数

public static void main(String args[]){int i,j;for(j=2;;j++)  {for(i=2;i<=j/2;i++) {if(j%i==0)break;}if(i>j/2)  {System.out.println(j);}}}

求质因子

public static void main(String[] args){int n = 0;String s = null;BufferedReader buf;buf=new BufferedReader(new InputStreamReader(System.in));System.out.print("请输入一个数：");try {s=buf.readLine();} catch (IOException e) {e.printStackTrace();}n=Integer.parseInt(s);int temp = n;for (int i = 2; i <= temp; i++){if (!isPrime(i)){continue;}while (true){if (temp%i == 0){temp = temp/i;System.out.println(i);}else {break;}}}}public static boolean isPrime(int n){int i;for (i = 2; i <= n; i++){if (n%i == 0){break;}}if (i >= n){return true;}else {return false;}}

0 0