java - 数学运算符

Question

我有这个方法会生成一个随机的数学表达式来解决它并将答案输出到一个变量:

public int Nov2()
{
    char[] ops = new char[] {'+', '-', '*', '/'};
    int i = rand.nextInt(4-0) + 0;
    char op1 = ops[i];

    int novnum1 = rand.nextInt(101-1) + 1;

    int novnum2 = rand.nextInt(101-1) + 1;

    int nov2result = 0;

    switch(op1) {
        case '+': nov2result = novnum1 + novnum2; break;
        case '-': nov2result = novnum1 - novnum2; break;
        case '*': nov2result = novnum1 * novnum2; break;
        case '/': nov2result = novnum1 / novnum2; break;
    }

    String nov2Exp = novnum1 + " " + op1 + " " + novnum2 + " = ";

    Nov2resstor = nov2result;

    setContentView(R.layout.gameview);

    TextView display = (TextView) findViewById(R.id.exp);

    display.setText(nov2Exp);

    return nov2result;
}

我将如何对具有两个以上术语的表达式使用相同类型的东西，而不必在我的下一个方法中编写非常复杂的 if 语句:

public int Eas3()
{
    char[] ops = new char[] {'+', '-', '*', '/'};
    int i = rand.nextInt(4-0) + 0;
    char op1 = ops[i];
    i = rand.nextInt(4-0) + 0;
    char op2 = ops[i];

    int easnum1 = rand.nextInt(101-1) + 1;

    int easnum2 = rand.nextInt(101-1) + 1;

    int easnum3 = rand.nextInt(101-1) + 1;

    int eas3result = 0;


    if (op1 == '+' && op2 == '+')
    {
        eas3result = ((easnum1 + easnum2) + easnum3);
    }
    else if (op1 == '+' && op2 == '-')
    {
        eas3result = ((easnum1 + easnum2) - easnum3);
    }
    else if (op1 == '+' && op2 == '*')
    {
        eas3result = ((easnum1 + easnum2) * easnum3);
    }
    else if (op1 == '+' && op2 == '-')
    {
        eas3result = ((easnum1 + easnum2) - easnum3);
    } 
.../

我有针对 2、3、4、5 和 6 执行此操作的方法，因此使用此方法我的 if 语句会变得非常大。

有什么想法吗？

Answer 1

您可以使用内置的 Javascript 引擎。

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

public class Test 
{
  public static void main(String[] args) throws Exception
  {
       ScriptEngineManager mgr = new ScriptEngineManager();
        ScriptEngine engine = mgr.getEngineByName("JavaScript");
        String foo = "40+2";
        System.out.println(engine.eval(foo));
    } 
}