Java Can'；我想不出这个密码。请给出一些见解

我不断收到错误

方法外接程序类DebugThree2无法应用于给定类型

，

二进制运算符“-”的操作数类型错误

// This application displays some math facts
public class DebugThree2 {

    public static void main(String args[]) {
      add();
      subtract();
      System.out.println("Java");
      int a = 2, b = 5, c = 10;
      add("a" + "b");
      add("b" + "c");
      subtract("c" - "a");            
    }

    public static void add() {
      System.out.println("The sum of " + "a" + "and" + "b" + "is" + "a" + "b");
    }

    public static void subtract() {
      System.out.println("The difference between " + "a" + "and" + "b" + "is" + "a" - "b");
    }
} 

我想这样的东西可能更适合你。您正试图从（字符串）a中减去（字符串）b

---

您必须使用它们的实际值，不包括引号

为什么将变量放在

“

”之间？为什么方法不接收任何参数？

public static void main(String args[])
{
  add();
  subtract();
  System.out.println("Java");
  int a = 2, b = 5, c = 10;
  add(a,b);
  add(b,c);
  subtract(c,a);            
}
public static void add(int a, int b)
{
  System.out.println("The sum of " + a +
     " and " +  b  + " is " + (a+b));
}
public static void subtract(int a, int b)
{
  System.out.println("The difference between " +
    a + " and  " + b + " is " + (a-b));
}

"a" - "b"