Java error: message "incompatible types"

Question

I get an error in Java at compile time:

UserID.java:36: error: incompatible types
            + generator.nextInt(10);
            ^
  required: String
  found:    int

Here is the Java code:

public class UserID {

  private String firstName; 
  private String userId;  
  private String password;

  public UserID(String first) {
     Random generator = new Random();

     userId = first.substring(0, 3) + 
        + generator.nextInt(1) + 
       (generator.nextInt(7) + 3) + generator.nextInt(10);     //this works

     password = generator.nextInt(10) + generator.nextInt(10);   //Error is here

  } 
}

What is the cause of this error and how to fix it? Why doesn't this automatically push int to String?

Answer 1

On the line, passwordyou add integers (when you want to concatenate them) and put them on the line without an explicit cast. You need to use Integer.toString ()

So,

password = Integer.toString(generator.nextInt(10) + generator.nextInt(10)
        + generator.nextInt(10) + generator.nextInt(10)
        + generator.nextInt(10) + generator.nextInt(10));

The reason it works in usernameis because you add strings for integers placed in a String, so it implicitly throws it into a String when concatenating.

Answer 2

It is best to use StringBuilder,

StringBuilder sb=new StringBuilder();
sb.append(first.substring(0, 3));
sb.append(last.substring(0, 3));
sb.append(generator.nextInt(1));
sb.append(generator.nextInt(7) + 3);
sb.append(generator.nextInt(10));

userId=sb.toString();

Answer 3

, "", :

password = "" + generator.nextInt(10) ...

Answer 4

Look at the type of the return value generator.nextInt(), it returns int, but you are trying to assign it Stringto what it says: an incompatible type, you cannot assign an int to String.