Java 我的随机数总是零?
我的程序运行得很好,除了我为数学游戏中的问题生成的随机数总是零。我不明白。我试过使用math.random,我也遇到了同样的问题。它在干什么Java 我的随机数总是零?,java,class,variables,random,Java,Class,Variables,Random,我的程序运行得很好,除了我为数学游戏中的问题生成的随机数总是零。我不明白。我试过使用math.random,我也遇到了同样的问题。它在干什么 import java.util.Scanner; import java.util.Random; public class Problem { private int numberOfQuestions; private int answer; private int userAnswer; private int
import java.util.Scanner;
import java.util.Random;
public class Problem {
private int numberOfQuestions;
private int answer;
private int userAnswer;
private int score;
private int max;
private int min;
private static String question;
Random rand = new Random();
Scanner input = new Scanner(System.in);
private int num1 = rand.nextInt((max - min) + 1) + min;
private int num2 = rand.nextInt((max - min) + 1) + min;
public Problem(int max, int min, int numberOfQuestions){
this.max = max;
this.min = min;
this.numberOfQuestions = numberOfQuestions;
}
public int multiplyNumbers()
{
answer = num1 * num2;
return answer;
}
public String multiplyQuestion(){
String sum = ("What is " + num1 + " * " + num2 + "?");
return sum;
}
public int addNumbers()
{
answer = num1 + num2;
return answer;
}
public String addQuestion(){
String sum = ("What is " + num1 + " + " + num2 + "?");
return sum;
}
public int subtractNumbers()
{
answer = num1 - num2;
return answer;
}
public String subtractQuestion(){
String sum = ("What is " + num1 + " - " + num2 + "?");
return sum;
}
public int divideNumbers()
{
answer = num1 / num2;
return answer;
}
public String divideQuestion(){
String sum = ("What is " + num1 + " / " + num2 + "?");
return sum;
}
public String answer(int min, int max, int numberOfQuestions){
int operator = (int)(Math.random()*4) + 1;
if(operator == 1){
question = addQuestion();
answer = addNumbers();
} else if(operator == 2) {
question = subtractQuestion();
answer = subtractNumbers();
} else if(operator == 3) {
question = divideQuestion();
answer = divideNumbers();
} else if(operator == 4) {
question = multiplyQuestion();
answer = multiplyNumbers();
}
System.out.println(question);
userAnswer = input.nextInt();
System.out.println(answer);
String result;
int score = 0;
if(userAnswer == answer){
score = score + 1;
result = "Correct. Score is currently: " + score + "/" + numberOfQuestions;
} else {
score = score - 1;
result = "Incorrect. Score is currently: " + score + "/" + numberOfQuestions;
}
return result;
}
public String toString(){
return "Math game~!" + answer(min, max, numberOfQuestions);
}
}
实例字段初始化表达式在构造函数主体之前执行。所以
private int num1 = rand.nextInt((max - min) + 1) + min;
被执行之前
this.max = max;
this.min = min;
在构造函数中
此时,max和min的值因此为默认值0。在赋值max和min之后,将num1的初始化语句移动到构造函数体。min和max作为值输入,但它们尚未给定值。还要注意的是,从某种意义上说,random并不是真正的随机,它需要一些东西来生成随机数,所以作为一个中断或者可能是什么,所以如果模式被发现,那么可以猜测代码从上到下运行。一旦你知道了这一点,答案应该是显而易见的。解决方案是将初始化移动到构造函数。