在 Java 中生成随机数学运算符
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Generate random math operator in Java
提问by Perception
I was wondering how I should initialize int c from the switch statement. I can't figure out how to "extract" the random switch-argument into the final answer. I am a beginner so maybe I am missing something obvious here. Here is the code that I have so far:
我想知道我应该如何从 switch 语句初始化 int c 。我不知道如何将随机切换参数“提取”到最终答案中。我是初学者，所以也许我在这里遗漏了一些明显的东西。这是我到目前为止的代码：
import java.util.*;
public class whileTest{
public static void main (String args[]){
Scanner sc = new Scanner(System.in);
String a;
do{
String operatorSwitch;
int b;
int c;
Random number = new Random();
int d = number.nextInt(100) +1;
int e = number.nextInt(100) +1;
Random operatorChoice = new Random();
int operator = operatorChoice.nextInt(4);
switch (operator){
case 0: operatorSwitch= "+";
c = d+e;
break;
case 1: operatorSwitch= "-";
c = d-e;
break;
case 2: operatorSwitch= "*";
c = d*e;
break;
case 3: operatorSwitch= "/";
c = d/e;
break;
default: operatorSwitch= "";
}
System.out.println("What is: "+d+operatorSwitch+e+"?");
b = sc.nextInt();
if(b!=c)
System.out.println("Wrong answer! Right answer is: "+c);
else{if(b==c)
System.out.println("Right answer!"+c);
}
System.out.println("Continue? y/n");
a = sc.next();
}while(a.equals("y"));
}
}
回答by Perception
As a practice, unless you have a good reason not too, you should always explicitly initialize your variables. In this case you want to change this:
作为一种实践，除非您有充分的理由不这样做，否则您应该始终显式初始化您的变量。在这种情况下，您要更改此设置：
String operatorSwitch;
int b;
int c;
To this:
对此：
String operatorSwitch = null;
int b = 0;
int c = 0;
The problem with your current code is a compilation one, due to the variable 'c' possiblynot being initialized.
您当前代码的问题是编译问题，因为变量 'c'可能未初始化。
回答by flup
Not sure how pretty you wish to make this but you could write an Operator interface with anonymous subclasses and pick a random index from those.
不确定您希望这样做有多漂亮，但您可以编写一个带有匿名子类的 Operator 接口，并从中选择一个随机索引。
interface Operator{
public int operateOn( int a, int b );
public char getDisplayChar();
}
Operator[] operators = {new Operator(){
public int operateOn(int a, int b){
return a + b;
}
public char getDisplayChar(){
return '+';
}
}, new Operator(){
public int operateOn(int a, int b){
return a - b;
}
public char getDisplayChar(){
return '-';
}
} // etc.
};
