題目

從鍵盤讀入個數不確定的整數，并判斷讀入的正數和負數的個數，輸入 為0時結束程序。

知識點

最簡單“無限” 循環格式：while(true) , for(;;),無限循環存在的原因是并不
知道循環多少次，需要根據循環體內部某些條件，來控制循環的結束。

while代碼

package lesson.l3_while;import java.util.Scanner;public class WhileDemo1 {public static void main(String[] args) {Scanner scanner=new Scanner(System.in);int positive=0;int negative=0;while (true){int num=scanner.nextInt();if (num>0){positive++;}else if (num<0){negative++;}else {break;}}System.out.println("positive:"+positive+"\t"+"negative:"+negative);scanner.close();}
}

for代碼

package lesson.l2_for;import java.util.Scanner;public class ForDemo7 {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int positive = 0;int negative = 0;for (;;){int num= scanner.nextInt();if (num>0){positive++;}else if (num<0){negative++;}else {break;}}System.out.println("positive:" + positive + "\t" + "negative:" + negative);scanner.close();}
}