Java的Set方法

Question

我是java新手，我创建了一个set method book reference number，所以它只接受3个字符。我尝试了下面的代码，但不正确

public void setRefNumber(String ref)
 {
  System.out.println("hello " + ref());
      if(ref.length() ==3)
{
        return;
 }
  System.out.println("Fail...Your reference number mis too short"); 
}

Answer 1

你的方法返回时什么也不做。在返回语句之前做你必须做的事情。此外，如果同时提供if和else部分，则在方法类型已经无效时，不必使用return

public void setRefNumber(String ref) {
  // it could be null too
  if ( ref == null ) {
   System.out.println("Cannot be null);
   return;
  }
  System.out.println("hello " + ref);
  if(ref.length() == 3) {
    // set ref here
    System.out.println("Success");
    // return;
  } else {
    System.out.println("Fail...Your reference number is too short/long"); 
  }
}

就像其他人指出的那样。ref是变量而不是方法。使用ref而不是ref（）

Answer 2

class Main {
  public static void main(String[] args) {
    setRefNumber("123");
    setRefNumber("1234");
    setRefNumber("12");
    setRefNumber("aa"); //to show you that you are not checking if the passed parameter is even a number currently
  }

  public static void setRefNumber(String ref) {
    if(ref.length() >= 3) {
      System.out.println("hello " + ref);
      return;
    } else {
      System.out.println("Fail...Your reference number " + ref + " is too short");
    }
  }
}

输出：

hello 123
hello 1234
Fail...Your reference number 12 is too short
Fail...Your reference number aa is too short

试试看here!