How to find a particular substring in a string without using any builtin methods of string

[amit kumar goyal]

Hi my question is how can we find a particular string in another string without using any inbuilt String class methods. for eg. string "cofee" inside "please give me a cup of cofee". Thanks

[Vinoth Thirunavukarasu]

What do you mean

amit kumar goyal wrote:how can we find a particular string in another string without using any inbuilt String

[Ankit Garg]

Hi Amit. Welcome to javaranch.

Well for that first you'll have to convert the string into a char array using, well a built in method of string class i.e. toCharArray and then implement a simple algorithm to search the char array. Or you can use the charAt method to check the characters at different indexes of the string and match it with corresponding characters of your other string. In both the cases you will have to use methods of the string class. I could have given you the exact code but here at ranch, we encourage people to try to solve simple problems like this on their own...

[amit kumar goyal]

means does that string "cofee" or for that matter any string is there in another string.......i hope you got that...

[amit kumar goyal]

Thanks for the reply....But i want a solution where we do not use any of the String class built in methods...

[Henry Wong]

amit kumar goyal wrote:Thanks for the reply....But i want a solution where we do not use any of the String class built in methods...

Well, if you can't call *any* methods of the string class, then I believe it is *not* possible, as you won't be able to extract the data. Heck, to print the string to the screen, the internal libraries even use some of the methods.

Henry

[Seetharaman Venkatasamy]

amit kumar goyal wrote:Thanks for the reply....But i want a solution where we do not use any of the String class built in methods...

why you want to do this? you want solution ? then how about this ?

  

        String str = "amit kumar goyal";
	StringBuilder builder = new StringBuilder(str);
	String sr = builder.substring(4, 8);//Here substring is  belong to the AbstractStringBuilder
	System.out.println(sr);

  

[amit kumar goyal]

I was asked this question in an interview.....Probably they want some solution like how it is implemented in the String class....the also asked a question like how can we find the length of a String without using any inbuilt methods......

[amit kumar goyal]

Anyways thanks everyone for the help......

[Henry Wong]

amit kumar goyal wrote:I was asked this question in an interview.....Probably they want some solution like how it is implemented in the String class....the also asked a question like how can we find the length of a String without using any inbuilt methods......

I think you are reading the question too strictly. I agree that they probably want some solution on how it is implemented -- which you should have answered... that is it held internally as a char array, and that you can get a copy of that array, using the toCharArray() method. I am sure that they don't mean that you can't call that method.

Then to answer the substring question, you need to talk about loops and checking characters.etc. For your second question, it is simply the length of the array.

Henry

[Rob Spoor]

As said before, you need at least toCharArray() or a combination of length() and charAt(int). Those are the only options to be able to inspect the contents of the strings.

Personally I would use length() and charAt(int) since it doesn't create a new char[].