Java error: "incompatible types" message

Question

I am getting an error in Java during compilation:

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 reason for this error and how do I fix it? Why is it not automatically promoting the int to a String?

In order to place an integer into a String you have two choices: 1. Integer.toString(yourint). and 2. Add blankstring to your integer like this String mystring = "" + 25. If you don't, the compiler will let you know that you've made a mistake. Rightly so, you are putting something where it doesn't belong. — Eric Leschinski
– Eric Leschinski, Commented Jul 31, 2014 at 15:37

Nicholas · Accepted Answer · 2011-09-19 03:23:24Z

9

On the password line, you're adding Integers(When you want to be concatenating them) and putting it into a string without an explicit cast.You'll have to use Integer.toString()

So like this

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 username is because you have Strings being added to integers the put into a String, so it's implicitly casting it to a String when concatinating.

answered Sep 19, 2011 at 3:23

Nicholas

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2 Comments

Michael Anderson Over a year ago

I Suspect the OP is trying to concatenate multiple ints as strings, rather than add them together then convert the sum to a single string. So he should be wrapping each generator.nextInt(X) in Integer.toString rather than the sum of them all.

Nicholas Over a year ago

Yes. I agree that his goal is concatination, but in it's current state it's adding them. The solution is either Integer.toString() to to add a "" + before the whole thing.

KV Prajapati · Accepted Answer · 2011-09-19 03:31:51Z

2

Better way is 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();

answered Sep 19, 2011 at 3:31

KV Prajapati

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Comments

JRL · Accepted Answer · 2011-09-19 03:28:18Z

1

Easy fix is to add "" first, e.g.:

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

answered Sep 19, 2011 at 3:28

JRL

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Comments

OscarRyz · Accepted Answer · 2011-09-19 03:32:22Z

0

Look at the return type of generator.nextInt() it returns an int but you're trying to assign it to a String that's what it says: incompatible type you can't assign an int to a String.

answered Sep 19, 2011 at 3:32

OscarRyz

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