100以内加减法运算

class  ExercisesDemo
{
public static void main(String[] args) 
{
int num1,num2,num3,num4;
String operator1,operator2;
num1 = getNumbers(100);
num2 = getNumbers(100);
num3 = getNumbers(100);
operator1 = getOperator();
operator2 = getOperator();
num4 = operate(num1,num2,num3,operator1,operator2);
if(num4 < 0 || num4 > 100)
{
System.out.println("所给题目不符合要求，请重试...");
}else
{
String arr[] = {String.valueOf(num1),String.valueOf(num2),String.valueOf(num3),String.valueOf(num4)};
int randomNumber;
randomNumber = getNumbers(4);
System.out.println("答案是：" + arr[randomNumber]);
arr[randomNumber]="()";
System.out.println ("Sum of these numbers : " + arr[0] + operator1 + arr[1] + operator2 + arr[2] + " = " + arr[3]);
}
}
static int getNumbers(int type)
{
return (int)((Math.random())*type);
}
static String getOperator()
{
String operator[]={"+","-"};
int num = getNumbers(2);
return operator[num];
}
static int operate(int num1,int num2,int num3,String operator1,String operator2)
{
if(operator1.equals("+") && operator2.equals("+"))  
        {  
           return num1 + num2 + num3;
}else
if(operator1.equals("+") && operator2.equals("-"))  
{  
return num1 + num2 - num3;
}else
if(operator1.equals("-") && operator2.equals("+"))  
{  
return num1 - num2 + num3;
}else
if(operator1.equals("-") && operator2.equals("-"))  
{  
return num1 - num2 - num3;
}
return 0;
}
}