CODEWITHSUNDEEP
javaarrayssearcharraylist
Tim Tolbert
Tim Tolbert

Reputation: 7

Having problems with a search method between Arrays and Array lists

OK so I'm trying to design a simple program that checks to see if a substring of length 4 characters is within all initial strings. Here is my code as follows:

public class StringSearch{
private String[] s1Array = {"A","C","T","G","A","C","G","C","A","G"};
private String[] s2Array = {"T","C","A","C","A","A","C","G","G","G"};
private String[] s3Array = {"G","A","G","T","C","C","A","G","T","T"};
//{for (int i = 0; i < s1Array.length; i++){
//    System.out.print(s1Array[i]);
//}}//check if Array loaded correctly
/**
 * This is the search method.
 * 
 * @param  length   length of sub string to search
 * @param  count    counter for search engine
 * @param  i        for-loop counter
 * @return subStr   returns strings of length = 4 that are found in all 3 input strings with at most 
 *                  one mismatched position.
 */
public String Search()
{
    int length = 4;
    int count = 0;
    int i = 0;
    ArrayList<StringSearch> subStr = new ArrayList<StringSearch>();
    //String[] subStr = new String[4];
    do
    {
    for (i = count; i < length; i++){
        subStr.add(s1Array[i]); // cant find .add method???
        count = count + 1;
    }
    if (s2Array.contains(subStr) && s3Array.contains(subStr)){ //can't find .contains method???
        System.out.println(subStr + "is in all 3 lists.");
    }
    if (count = s1Array.length){
        System.out.println("Task complete.");
    }
    else{
        count = count - length;
        count = count + 1;
    }
    }while (count <= s1Array.length);
}

}

For some reason, Java cannot seem to find the .add or .contains methods and I have no idea why. So my approach was to turn the initial Strings each into an array (since the assignment specified each string would be exactly N elements long, in this case N = 10) where 1 letter would be 1 element. The next thing I did was set up a for loop that would scan s1Array and add the first 4 elements to an ArrayList subStr which is used to search s2Array and s3Array. Here is where .add isn't a valid method, for whatever reason. Commenting that out and compiling again, I also ran into an issue with the .contains method not being a valid method. Why won't this work? What am I missing? Logically, it seems to make sense but I guess maybe I'm missing something in the syntax? Help would be appreciated, as I'm a Java novice.

Upvotes: 0

Views: 93

Answers (4)

Dave S
Dave S

Reputation: 3468

There are lots of errors and misunderstandings here.

Let's start with #1

private String[] s1Array = {"A","C","T","G","A","C","G","C","A","G"};

Making an array of strings is just silly, you should either use a single string or an array of characters.

private String s1 = "ACTGACGCAG";

Or

private char[] s1Array = {'A','C','T','G','A','C','G','C','A','G'};

Now #2

ArrayList<StringSearch> subStr = new ArrayList<StringSearch>();

This means you are trying to make an ArrayList that contains objects of type StringSearch. StringSearch is a class that contains your three arrays and your Search function so I don't think this is what you want.

If you wanted to make a list of 3 strings you might do something like this:

ArrayList<String> stringList = new ArrayList<String>();
stringList.add(s1);
stringList.add(s2);
stringList.add(s3);

Now say you defined s1, s2 and s3 as strings you can do something like this.

for(int i = 0; i <= s1.length() - 4; i++)
{
    String subStr = s1.substring(i, i + 4);
    if(s2.contains(subStr) && s3.contains(subStr))
    {
        System.out.println(subStr + " is in all 3 lists.");
    }
}
System.out.println("Task Complete.");

The above code should achieve what it looks like you are trying to do. However, it should be noted that this isn't the most efficient way, just a way, of doing it. You should start with some more basic concepts judging by the code you have so far.

Upvotes: 1

Shababb Karim
Shababb Karim

Reputation: 3733

First of all you need to educate yourself on the concept of Java generics. The most basic thing about generics is that once you declare a collection, here it is the arraylist, as you can only add objects of StringSearch.
Second of all, logically what you can do is to implement an algorithm called Longest Common Subsequence. Check in pairs whether the longest subsequeces are 4 or not on the arrays.

Upvotes: 0

Sterls
Sterls

Reputation: 761

Instead of:

ArrayList<StringSearch> subStr = new ArrayList<StringSearch>();

Replace it with:

String subStr = "";

And within the for loop to get the first 4 letters in s1 to be in its own string (subStr) add the line: 

subStr += s1Array[i];

Also, s1Array is a String array, and not a String. The .contains method is a method that belongs to String variables, so for eg. the way you have it implemented, you can say s1Array[i].contains. But you cannot say s1Array.contains. If you change your String arrays to Strings and edit your code to suit, everything should work the way you expect it to work.

Upvotes: 0

rastik
rastik

Reputation: 2576

After declaring subStr as ArrayList you can call add or contains only with StringSearch objects as parameters.

Upvotes: 0

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