Android随机生成方程式答案

Question

我正在创建一个程序，其中存在随机生成的数字和随机生成的操作数，具体取决于用户选择的难度。我已经完成了数字和操作数的随机部分，但无法弄清楚如何计算出答案。任何帮助，将不胜感激。 谢谢。

   public void generateNumbers(int diff) {

    switch (diff) {


        // Novice difficulty
        case 0:
            Random r = new Random();
            Random x = new Random();
            Random RandomOperand = new Random();
            oper = operands[RandomOperand.nextInt(operands.length)];
            Log.d("Brain Trainer", "operand = " + oper);
            equation.setText("  " + r.nextInt(200) + " " + oper + " " + x.nextInt(200) + " =" + " ?");
            break;
        // Easy difficulty
        case 1:
            Random ran = new Random();
            int p = ran.nextInt(2);
            Log.d("Brain Trainer", "Random num = " + p);
            switch (p) {
                case 0:
                    r = new Random();
                    x = new Random();
                    RandomOperand = new Random();
                    oper = operands[RandomOperand.nextInt(operands.length)];
                    equation.setText("  " + r.nextInt(200) + " " + oper + " " + x.nextInt(200) + " =" + " ?");
                    break;

                case 1:
                    r = new Random();
                    x = new Random();
                    Random z = new Random();
                    RandomOperand = new Random();
                    oper = operands[RandomOperand.nextInt(operands.length)];
                    oper1 = operands[RandomOperand.nextInt(operands.length)];
                    equation.setText("  " + r.nextInt(200) + " " + oper + " " + x.nextInt(200) + " " + oper1 + " " + z.nextInt(200) + " =" + " ?");
                    break;
            }
            break;
        //Medium difficulty
        case 2:
            ran = new Random();
            p = ran.nextInt(3);
            Log.d("Brain Trainer", "Random num = " + p);
            switch (p) {
                case 0:
                    r = new Random();
                    x = new Random();

                    RandomOperand = new Random();
                    oper = operands[RandomOperand.nextInt(operands.length)];
                    equation.setText("  " + r.nextInt(200) + " " + oper + " " + x.nextInt(200) + " =" + " ?");
                    break;
                case 1:
                    r = new Random();
                    x = new Random();
                    Random z = new Random();
                    RandomOperand = new Random();
                    oper = operands[RandomOperand.nextInt(operands.length)];
                    oper1 = operands[RandomOperand.nextInt(operands.length)];
                    equation.setText("  " + r.nextInt(200) + " " + oper + " " + x.nextInt(200) + " " + oper1 + " " + z.nextInt(200) + " =" + " ?");
                    break;
                case 2:
                    r = new Random();
                    x = new Random();
                    z = new Random();
                    Random c = new Random();
                    RandomOperand = new Random();
                    oper = operands[RandomOperand.nextInt(operands.length)];
                    oper1 = operands[RandomOperand.nextInt(operands.length)];
                    oper2 = operands[RandomOperand.nextInt(operands.length)];
                    equation.setText("  " + r.nextInt(200) + " " + oper + " " + x.nextInt(200) + " " + oper1 + " " + z.nextInt(200) + " " + oper2 + " " + c.nextInt(200) + " =" + " ?");
                    break;
            }
            break;

        // Guru difficulty
        case 3:
            ran = new Random();
            p = ran.nextInt(3);
            Log.d("Brain Trainer", "Random num = " + p);
            switch (p) {
                case 0:
                    r = new Random();
                    x = new Random();
                    Random z = new Random();
                    Random c = new Random();
                    RandomOperand = new Random();
                    oper = operands[RandomOperand.nextInt(operands.length)];
                    oper1 = operands[RandomOperand.nextInt(operands.length)];
                    oper2 = operands[RandomOperand.nextInt(operands.length)];
                    equation.setText("  " + r.nextInt(200) + " " + oper + " " + x.nextInt(200) + " " + oper1 + " " + z.nextInt(200) + " " + oper2 + " " + c.nextInt(200) + " =" + " ?");
                    break;
                case 1:
                    r = new Random();
                    x = new Random();
                    z = new Random();
                    c = new Random();
                    Random v = new Random();
                    RandomOperand = new Random();
                    oper = operands[RandomOperand.nextInt(operands.length)];
                    oper1 = operands[RandomOperand.nextInt(operands.length)];
                    oper2 = operands[RandomOperand.nextInt(operands.length)];
                    oper3 = operands[RandomOperand.nextInt(operands.length)];
                    equation.setText("  " + r.nextInt(200) + " " + oper + " " + x.nextInt(200) + " " + oper1 + " " + z.nextInt(200) + " " + oper2 + " " + c.nextInt(200) + oper3 + " "
                            + v.nextInt(200) + " =" + " ?");
                    break;
                case 2:
                    r = new Random();
                    x = new Random();
                    z = new Random();
                    c = new Random();
                    v = new Random();
                    Random h = new Random();
                    RandomOperand = new Random();
                    oper = operands[RandomOperand.nextInt(operands.length)];
                    oper1 = operands[RandomOperand.nextInt(operands.length)];
                    oper2 = operands[RandomOperand.nextInt(operands.length)];
                    oper3 = operands[RandomOperand.nextInt(operands.length)];
                    oper4 = operands[RandomOperand.nextInt(operands.length)];
                    equation.setText("  " + r.nextInt(200) + " " + oper + " " + x.nextInt(200) + " " + oper1 + " " + z.nextInt(200) + " " + oper2 + " " + c.nextInt(200) + " " +
                            " " + oper3 + " " + v.nextInt(200) + " " + oper4 + v.nextInt(200) + " =" + " ?");
                    break;
            }
            break;

    }
}

Answer 1

无论您生成的等式是什么，您可能需要以下列方式将该表达式的结果存储为特定类的数据成员：

使用JDK1.6 +，您可以使用内置的Javascript引擎。如，

import javax.script.ScriptEngineManager;
import javax.script.ScriptEngine;

public class App{
public static void main(String args[]) throws Exception{
    ScriptEngineManager manager = new ScriptEngineManager ();
    ScriptEngine engine = manager.getEngineByName("JavaScript");
    System.out.println(engine.eval("2+2"));
  }
}