Filter a string array from another one

i m little bit confused related to string function I have one array of string Example

String Array1[]=new String[10];
Arra开发者_运维百科y1[0]="Hello";

String Array2[]=new String[10];
Array2[0]="Hello my world";
Array2[1]="Hi buddy";

I want to filter the string Array1[0] from Array2 That is, in which index of Array2 the string "Hello" appears.

   /**
     * This method searches for key in the array of String , starts looking from fromIndexSpecified
     * @param source
     * @param key
     * @param fromIndex
     * @return
     */
    private static int findIndexOfKey(String[] source, String key, int fromIndex) {

        if (fromIndex > source.length) {
            return -1;// invalid arg ..can also throw IlligleArgumentException
        }
        for (int index = fromIndex; index < source.length; index++) {
            if (source[index].indexOf(key) > -1) {
                return index;//found..!
            }
        }
        return -1; //no match found
    }

You would need to loop through the items in Array2 and do a substring comparison:

private int findIndexOfSubstring(array, target) {
   for (int i=0; i<array.size(); i++) {
      if array[i].indexOf(target)>-1 return i; //element of Array2 contains target in it.
   }
   return -1; //no match found
}

//somewhere else
String Array1[]=new String[10];
Array1[0]="Hello";

String Array2[]=new String[10];
Array2[0]="Hello my world";
Array2[1]="Hi buddy";

int answer = findIndexOfSubstring(Array2, Array1[0]);

A String[] is actually an Array of Strings. So it can hold multiples Strings. For example:

String[] stringArray = new String[2];
stringArray[0] = "My String 1";
stringArray[1] = "My String 2";

If you want to find out the first index of an String array that contains a substring you need to do something like:

   int findFirst(String subString, String[] stringArray) {
        for (int i = 0; i < stringArray.length; i++) {
            if (stringArray[i].contains(subString)) {
                return i;
            }
        }
        // indicates that no String in the array contained the subString
        return -1;
    }

And here is the way to use the method:

int firstIndex = findFirst("String 2", stringArray);

Iterate over the second array, check every time:

for(int i = 0; i < Array2.length; i++) {
if(Array2[i].contains(Array1[0]) {
 //your logic here
System.out.println("Found match at position " + i);

}
}

Edit: be sure that in your given case Null-Pointer-Exceptions can occur. Perhaps add

if(Array2[i] != null)

You can use the method indexOf from Apache Commons ArrayUtils class.

Usage:

String[] array1 = new String[10];
array1[0] = "Hello";

String[] array2 = new String[10];
array2[0] = "Hello my world";
array2[1] = "Hi buddy";

int index = ArrayUtils.indexOf(array2, array1[0]);