Java中產生隨機數的方法
1、調用System.currentTimeMillis()
方法可以獲取1970年1月1日午夜到現在的毫秒數(例如:1203183086328毫秒),我們可以通過取餘的方式得到其最後一位的整數:
int number1 = (int)(System.currentTimeMillis() % 10);
案例:通過程序產生隨機數讓一年級學生練習加法。程序隨機產生兩個一位整數,number1和number2,然後顯示“What is 1 + 7?”
package program3_1;
import java.util.Scanner;
public class AdditionQuiz {
public static void main(String[] args) {
int number1 = (int)(System.currentTimeMillis() % 10);
int number2 = (int)(System.currentTimeMillis() / 7 % 10);
Scanner input = new Scanner(System.in);
System.out.print("What is " + number1 + " + " + number2 + " ?");
int answer = input.nextInt();
System.out.println(number1 + " + " + number2 + " = " + answer + " is " + (number1 + number2 == answer));
}
}
2、使用Math.random()來獲得一個0.0到1.0之間的隨機double值,不包括1.0。通過(int)(Math.random() * 10)
會返回一個隨機的一位整數(即0到9之間的數)
int number1 = (int)(Math.random() * 10);
案例:一個讓一年級學生練習減法的程序,程序隨機產生兩個一位整數number1和number2,且滿足number>=number2。顯示問題:“What is 9 - 2 ?”學生輸入答案後,顯示消息判斷是否正確
package program3_3;
import java.util.Scanner;
public class SubtractionQuiz {
public static void main(String[] args) {
int number1 = (int)(Math.random() * 10);
int number2 = (int)(Math.random() * 10);
if(number1 < number2) {
int temp = number1;
number1 = number2;
number2 = temp;
}
System.out.println("What is " + number1 + " - " + number2 + " ?");
Scanner input = new Scanner(System.in);
int answer = input.nextInt();
if(number1 - number2 == answer) {
System.out.println("You are correct!");
}
else {
System.out.println("You are wrong!");
System.out.println(number1 + " - " + number2 + " should be " + (number1 - number2) + "!");
}
}
}
大家如果還有什麼問題、建議或者補充可以留言,看到了我會及時回覆!