using string indexOf java

Question

im doing a program where i need to return the index of MyString of the first occurence. idk how to use the indexof in this situation. i think it might be something like ch = indexof[] but im not sure. im still new at this and the api didnt help me much

/*********************************************************************************
     This program will create classes that do similar operations to the Java String

     Javier Perez
     csc110
     11/5/12
    *********************************************************************************/
    package string.assignment;
    public class MyString
    {

        private char[] array;
        private int size;
        private int max;

        public MyString()
        {
            array = new char[25];
            max = 25;
        }
        public void setString(String newString)
        {
         if(newString.length() > 25)
         {
             System.out.println("/nEnter a number equal or less than 25 " );

         }
         else
         {
          for(int i=0; i < newString.length(); i++)
          {
            array[i] = newString.charAt(i);
          }
         }
        }


        public String toString()
        {
            return new String(array);
        }

        public char charAt(int index)
        {
            return array[index];
        }

        public boolean contains(char ch)
        {
            for(char c: array)
            {
                if(c == ch) return true;
            }
            return false;
        }
        public int indexOf( char ch )
        {
            ch = ch.indexOf();

        }
        return index; 


    }

@javip.. No your current code would not compile. Your last return statement is outside your method indexOf. May be you posted it wrong here. — Rohit Jain
– Rohit Jain, Commented Nov 13, 2012 at 5:25
@Xymostech.. No need of documentation of string.indexOf here. OP is implementing it using character array. — Rohit Jain
– Rohit Jain, Commented Nov 13, 2012 at 5:31

Rohit Jain · Accepted Answer · 2012-11-13 05:23:38Z

1

For fetching the index of a certain character from your array, you would have to iterate over the array, and compare each character with the one you want to check. If any character matches, return the index immediately.

Also, your last return statement should be inside your method, else your code would not compile.

So, your indexOf method in its simplest would be like this: -

public int indexOf( char ch ) {
    for (int i = 0; i < array.length; i++) {
        if (array[i] == ch) {
            return i;   // Character found, return current index
        }
    }
    return -1;    // Character not found. Return -1
}

answered Nov 13, 2012 at 5:23

Rohit Jain

214k45 gold badges419 silver badges534 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Yogendra Singh · Accepted Answer · 2012-11-13 05:24:57Z

1

Iterate your array of characters, match the desired character against the character at index in the array. If match found, not the position in the index variable which has default value as -1 and break the loop. Return the index value from the method.

     public int indexOf( char ch ){
        int index = -1;
        for(int i=0; i < array.length; i++){
         if(array[i] == ch){
             index = i;//first match found, stop searching
             break;
         }
       }
       return index; 
     }

This way, it returns the first matching position of the character in the string's character array, otherwise returns -1.

answered Nov 13, 2012 at 5:24

Yogendra Singh

34.5k7 gold badges66 silver badges73 bronze badges

Comments

John3136 · Accepted Answer · 2012-11-13 05:25:46Z

1

If it does indeed compile then your cut and paste is bad - what is that return index doing at the end?

Anyway - not I've used your own charAt rather than just a char compare.

    public int indexOf( char ch )
    {
        int result = -1;
        for(int i = 0; i <  size; i++) {
            if (charAt(i) == ch) {
                result = i;
                break;
            }
        }
        return result;

    }

answered Nov 13, 2012 at 5:25

John3136

29.3k4 gold badges55 silver badges77 bronze badges

Collectives™ on Stack Overflow

using string indexOf java

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related