題目：求0，1，2，3，4，5，6，7所能組成的8位奇數(shù)個數(shù)。
public?class?Subject41?{????public?static?void?main(String[]?args)?{????????int[]?arr?=?new?int[]{0,1,2,3,4,5,6,7};????????compose(arr);????}????????private?static?void?compose(int[]?arr)?{????????????????int?oddCount?=?0;????????for?(int?i?=?0;?i?<?arr.length;?i++)?{????????????if(!isParity(arr[i])){????????????????oddCount++;????????????}????????}????????????????int?num?=?factorial(arr.length-1);????????????????System.out.println("以下數(shù)字：");????????printArray(arr);????????System.out.println("可產(chǎn)生的奇數(shù)個數(shù)："+oddCount*num);????}????????private?static?boolean?isParity(int?num)?{????????if(num%2?==?1){????????????return?false;????????}else?{????????????return?true;????????}????}????????public?static?int?factorial(int?num){????????if(num?==?1){????????????return?1;????????}else{????????????return?num*factorial(num-1);????????}????}????????private?static?void?printArray(int[]?arr)?{????????for?(int?i?=?0;?i?<?arr.length?;?i++)?{????????????System.out.print(arr[i]+"?");????????}????}}運行結(jié)果：
題目：輸入一個偶數(shù)，判斷該偶數(shù)等于哪兩個素數(shù)之和。
import?java.util.ArrayList;import?java.util.List;import?java.util.Scanner;public?class?Subject42?{????public?static?void?main(String[]?args)?{????????System.out.println("請輸入大于等于2的偶數(shù)：");????????Scanner?scanner?=?new?Scanner(System.in);????????int?num?=?scanner.nextInt();????????getTwoPrimeNum(num);????}????????private?static?void?getTwoPrimeNum(int?num)?{????????List?primeNumberList?=?getPrimeNumber(2,num);????????for?(int?i?=?0;?i?<?primeNumberList.size();?i++)?{????????????for?(int?j?=?i;?j?<?primeNumberList.size();?j++)?{????????????????if(num?==?primeNumberList.get(i)?+?primeNumberList.get(j)){????????????????????System.out.println("該偶數(shù)為素數(shù)（"+primeNumberList.get(i)+"）和素數(shù)（"+primeNumberList.get(j)+"）的和");????????????????}????????????}????????}????}????????public?static?List?getPrimeNumber(int?a,?int?b){????????List?primeNumberList?=?new?ArrayList<>();????????if(a?>=?b){????????????System.out.println("a不能大于等于b！");????????}????????for(int?i=a;i<=b;i++){????????????if(isPrimeNumber(i)){????????????????primeNumberList.add(i);????????????}????????}????????return?primeNumberList;????}????????private?static?boolean?isPrimeNumber(int?i)?{????????boolean?flag?=?true;????????for(int?j=2;j?<=?i/2;j++){????????????if(i%j?==?0){????????????????flag?=?false;????????????????break;????????????}????????}????????return?flag;????}}運行結(jié)果：
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