package hello;
import java.util.Scanner;
public class hey {
  public static void main(String[] args) {
    double a,b,c;
    while(true) {
      System.out.println("请输入a:");
      Scanner sc=new Scanner(System.in);
      a=sc.nextDouble();
      System.out.println("请输入b:");
      Scanner sc1=new Scanner(System.in);
      b=sc.nextDouble();
      System.out.println("请输入c:");
      Scanner sc2=new Scanner(System.in);
      c=sc.nextDouble();
      if(b*b-4*a*c<0) {
        System.out.println("该方程无解");
        break;
      }
      else if(a==0&&b==0)
      {
        System.out.println("x任意解");
        break;
      }
      else {
        if(a==0) {
          System.out.println("x无解");
          break;
        }
        else {
        double X1=(-b+Math.sqrt(b*b-4*a*c))*1/(2*a);
        double X2=(-b-Math.sqrt(b*b-4*a*c))*1/(2*a);
        System.out.println("方程的根为："+X1);
        System.out.println("方程的根为："+X2);
        break;
        }
  } 
    }
  }
      }

package hello;
import java.util.Scanner;
public class hello {
  static Scanner scanner = new Scanner(System.in);
  public static void main(String[] args) {
    int n = 0;
    int a, b;
    int sum = 0;
    System.out.println("输入要做的题目的数量:");
    n = scanner.nextInt();
    int[] op = new int[n];
    int[] s = new int[n];
    int[] result = new int[n];
    String[] questions = new String[n];
    for (int i = 0; i < n; i++) {
      op[i] = (int) (Math.random() * 4); // 运算符
      a = (int) (Math.random() * 89) + 10; // 数a
      b = (int) (Math.random() * 89) + 10; // 数b
      System.out.println(a + getOp(op[i]) + b + "=?");
      System.out.println("输入答案:");
      s[i] = scanner.nextInt(); // 输入的答案
      result[i] = jisuan(a, b, op[i]); // 正确答案
      if (s[i] == result[i]) {
        sum++;
      }
      questions[i] = a + getOp(op[i]) + b + "=" + result[i];
    }
    // 最后的输出
    System.out.println("你答对了" + sum + "道题，答错了" + (n - sum) + "道题");
    for (int i = 0; i < n; i++) {
      System.out.print(questions[i]);
      if (s[i] == result[i]) {
        System.out.println(",你的回答是" + s[i] + "，正确");
      } else {
        System.out.println(",你的回答是" + s[i] + "，错误");
      }
    }
  }
  // 获取运算符
  private static String getOp(int index) {
    String string = "";
    switch (index) {
    case 0:
      string = "+";
      break;
    case 1:
      string = "-";
      break;
    case 2:
      string = "*";
      break;
    case 3:
      string = "/";
      break;
    }
    return string;
  }
  // 计算答案
  private static int jisuan(int a, int b, int index) {
    int sum = 0;
    switch (index) {
    case 0:
      sum = a + b;
      break;
    case 1:
      sum = a - b;
      break;
    case 2:
      sum = a * b;
      break;
    case 3:
      sum = a / b;
      break;
    }
    return sum;
  }
}