StringIndexOutOfBoundsException: String index out of range

[barry richard]

Hi, beginner here

This is the code that I am trying to run

import java.util.Scanner;

public class Example 
{
	static Scanner sc = new Scanner(System.in);
	
	public static void main(String [] args)
	{
		String str;
		int count;
		char letter;
		
		System.out.print("Enter a string: ");
		str = sc.nextLine();
		str = str.toUpperCase();
		
		count = 0;
		
		
		for(letter = 'A'; letter <= 'Z'; letter++)
		{
			for(int i = 0; i <= str.length(); i++)
			{
				if (letter == str.charAt(i))
				{
					System.out.println(letter);
					System.out.print(' ');
					count++;
					break;
				}
			}
			
		}
		System.out.println();
		System.out.println();
		System.out.println("There were " + count + " different letters");
	
	}
	

}

It is supposed to count all different letters in a string

This is what i get

Enter a string: hello
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 5
	at java.lang.String.charAt(String.java:658)
	at Example.main(Example.java:25)

What am I doing wrong

thanks for your time

[Jeff Verdegan]

The error message is telling you exactly what you're doing wrong.

It's telling you that at line 25 of Example.java, you're calling String.charAt(), and you're trying to get the 6th character (at index 5) of a String that has fewer than 6 characters.

So you need to either user a longer String, or not try to get the 6th character.

[Winston Gutkowski]

barry richard wrote:It is supposed to count all different letters in a string
What am I doing wrong

Simply put, you're NOT counting the number of different (by which I presume you mean distinct) letters in the String.

Forget about letters for a moment and consider how you would count the number of distinct values in ANY kind of set.

Dunno about you, but if it was me, I'd look at it as something like:
{number of distinct values} = {number of actual values} - {number of duplicate values}

So now all you have to work out is how to determine a "duplicate".

HIH

Winston

[Jeff Verdegan]

Try this:

public class Foo {
  public static void main(String[] args) {
    String s = "abc";
    System.out.println("length = " + s.length());
    
    for (int i = 0; i <= s.length(); i++) {
      System.out.print(i + ": ");
      System.out.flush();
      System.out.println(s.charAt(i));
    }
  }
}

[fred rosenberger]

don't you want

 for (int i = 0; i < s.length(); i++) {  

less than s.length(), not less than or equal to s.length()

[Jeff Verdegan]

fred rosenberger wrote:don't you want

 for (int i = 0; i < s.length(); i++) {  

less than s.length(), not less than or equal to s.length()

No, I want it exactly as it is. It's an SSCCE to show him what his code is doing.

[barry richard]

Thanks for your answers guys
Jeff, when I run your code

    public class Foo {  
      public static void main(String[] args) {  
        String s = "abc";  
        System.out.println("length = " + s.length());  
          
        for (int i = 0; i <= s.length(); i++) {  
          System.out.print(i + ": ");  
          System.out.flush();  
          System.out.println(s.charAt(i));  
        }  
      }  
    }  

I still get

length = 3
0: a
1: b
2: c
3: Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 3
	at java.lang.String.charAt(String.java:658)
	at Example.main(Example.java:12)

[Jeff Verdegan]

barry richard wrote:Thanks for your answers guys
Jeff, when I run your code

    public class Foo {  
      public static void main(String[] args) {  
        String s = "abc";  
        System.out.println("length = " + s.length());  
          
        for (int i = 0; i <= s.length(); i++) {  
          System.out.print(i + ": ");  
          System.out.flush();  
          System.out.println(s.charAt(i));  
        }  
      }  
    }  

I still get

length = 3
0: a
1: b
2: c
3: Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 3
	at java.lang.String.charAt(String.java:658)
	at Example.main(Example.java:12)

Yes, I know. That's what it's supposed to do. It's your code, with print statements added, so that you can see where you're going wrong. Look at it closely. Make sure you understand how the for loop control corresponds to the output we're seeing.

In particular, note that an array of length 3 has indices 0, 1, and 2. If it had index 3, it would have a lenght of 4.

[barry richard]

Ok I get it, it is an issue with index numbers being less than the length

like:
length = 5
index 0 to 4

[fred rosenberger]

barry richard wrote:
I still get

length = 3
0: a
1: b
2: c
3: Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 3
	at java.lang.String.charAt(String.java:658)
	at Example.main(Example.java:12)

so put it another way...what do you expect to print for s.charAt(3);, if you have already printed the a, b, and the c?

update - you replied while i was typing mine...

barry richard wrote:Ok I get it, it is an issue with index numbers being less than the length

correct. The standard idiom would be to loop to LESS THAN the length:

for (int i = 0; i < s.length(); i++) { 
...etc

[Jeff Verdegan]

fred rosenberger wrote:
so put it another way...what do you expect to print for s.charAt(3);, if you have already printed the a, b, and the c?

Well put. I need to learn to be more succinct like that.

[barry richard]

Thanks

I am learning java as my first language all by myself (I know!)

So I think I will be making some (actually a lot!) of silly mistakes along the way.

But i will get there. I always have.