Java String Limit

Question

I am new to java (previously only worked with sql) and I am attempting to set a length limit for my string variable. Basically I have a username field that can only be 6 characters long.

I am trying the following:

private String username (6);

I am assuming this is not the correct format. Does anyone know how i can do this in java correctly?

score 4 · Answer 1 · edited May 23 '17 at 12:08

Some other answers have claimed that "There is no way to limit Strings in java to a certain finite number through inbuilt features", and suggested rolling ones own. However, Java EE validations API is meant for just this. An example:

import javax.validation.constraints.Size;

public class Person {
      @Size(max = 6)
      private String username;
}

Further info on how to use Validation API, see this thread for example. Hibernate validator is the reference implementation (usage).

In short, when annotating an object as @Valid, validations done in annotations will be enforced.

score 2 · Answer 2 · answered Mar 31 '13 at 08:31

There is no way to limit Strings in java to a certain finite number through inbuilt features. Strings are immutable and take the value that you provide in their constructor. You will need to write code manually to do this.

Use the length() function to determine the length of the String and do not allow lengths greater than 6.

if( username.length() > 6 )
{
    throw new RuntimeException("User name too long");
}

One of the options you have is to throw an exception and then handle it elsewhere. Or you can display an alert to the user immediately after you encounter the problem.

score 1 · Answer 3 · answered Mar 31 '13 at 07:44

1

What you suggested is not the correct way to do what you want. Try using:

private int stringLimit = 6;
// Take input from user
private String username = inputString.substring(0,stringLimit);

For example:

inputString = "joelspolsky";
private String username = inputString.substring(0,stringLimit);
// username is "joelsp"

answered Mar 31 '13 at 07:44

stevenelberger

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2

This will blow up if the string is shorter than stringLimit. – user1944491 Oct 18 '15 at 19:54

score 1 · Answer 4 · answered Mar 31 '13 at 07:44

You can try soemthing like this:Take input from user then validate that string by using following function.

String output ="";
public boolean set(String str, int limit){
      if(str.length() <= limit){
            output= str;
            return true;
      }
      else
        return false;
 }

Andremoniy · Answer 5 · 2022-01-19T10:58:30.840

In this case annotation mechanism can be useful, if, of course, you know what this is.

You can create your own annotation, something like:

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface MaxLength {
    int value();
}

And use it like:

@MaxLength(6)
private String username;

Then you have to post-process such objects in a special post-processor, which you have to create manually.

score 0 · Answer 6 · answered Jan 30 '19 at 13:49

SubString() won't be suitable for this. If the length of input string is less than limit StringIndexOutOfBoundsException will be thrown. I think you can use StringBuilder for this.

StringBuilder buider = new StringBuilder(username);
builder.setLength(6);
String restName = builder.toString().trim();

ivan · Answer 7 · 2016-07-19T01:01:01.407

example to cut the length of URL

if (getURLitem.length() >= 15) {
                int stringLimit = 15;
                final String smallURL = getURLitem.substring(0, stringLimit);
                //show short string in textview...

                TextView urlLink = (TextView) findViewById(R.id.url_link);
                urlLink.setText(smallURL);

                // Set On click listener and open URL below
                ...........
            } else {
                //show full string in textview...
                TextView urlLink = (TextView) findViewById(R.id.url_link);
                urlLink.setText(getURLitem);

                // Set On click listener and open URL below
                ...........
            }

I assume `getString` is a variable name. Let me tell you that is a really bad variable name, because their names shouldn't start with a verb, it sounds like it is a method, which can be confusing. And please don't just post code, try to explain what is the solution you are providing, remember you are here to help others :) — Alonso Urbano, Jul 19 '16 at 00:32

Java String Limit

7 Answers7