How to check Strings equality which are in Uppercase and Lower Case using List Contains Method

Question

Please Suggest How to check Strings equality which are in Uppercase and Lower Case using List Contains Method

example:-

    List ll = new  ArrayList();
    ll.add("WWW");
    ll.add("XXX");
    ll.add("YYY");
    ll.add("ZZZ");


    System.out.println(ll.contains("xxx")); // Which returns the false I wanna return true Here

Here My List Size is Much Bigger Means around 1000000 , So I cannot use the For Loop to check String using equalsIgnoreCase, Also I doesnt Wants to Write My custom List.

I don't wants to iterate the ArrayList and Check One By One does It Possible ?? — Omkar More, Dec 13 '16 at 10:20

score -1 · Accepted Answer · answered Dec 13 '16 at 10:18

You can't avoid for loop. Even "basic" contains method uses for loop to compare each element of a list.

Here's contains method code of ArrayList class :

    /**
     * Returns <tt>true</tt> if this list contains the specified element.
     * More formally, returns <tt>true</tt> if and only if this list contains
     * at least one element <tt>e</tt> such that
     * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
     *
     * @param o element whose presence in this list is to be tested
     * @return <tt>true</tt> if this list contains the specified element
     */
    public boolean contains(Object o) {
        return indexOf(o) >= 0;
    }

    /**
     * Returns the index of the first occurrence of the specified element
     * in this list, or -1 if this list does not contain the element.
     * More formally, returns the lowest index <tt>i</tt> such that
     * <tt>(o==null&nbsp;?&nbsp;get(i)==null&nbsp;:&nbsp;o.equals(get(i)))</tt>,
     * or -1 if there is no such index.
     */
    public int indexOf(Object o) {
        if (o == null) {
            for (int i = 0; i < size; i++)
                if (elementData[i]==null)
                    return i;
        } else {
            for (int i = 0; i < size; i++)
                if (o.equals(elementData[i]))
                    return i;
        }
        return -1;
    }

Thnxxx So i have to write Custom List And use Equal IgnoreCase for String Equality. — Omkar More, Dec 13 '16 at 11:16
Not completely right I afraid: the first premise of this ticket is that list contains such an amount of elements that looping through it and to use the equalsIgnoreCase is not a solution. Well, I do not share this opinion but if we have to accept this starting point, your solution would only avoid the loop overriding the method to add a comparison with null and equals.Case differences would not be considered so it would not work fine. In addition to this this option means to create a custom List from AbstractList which all advantages and disadvantages related to in design and development — Facepalmed, Dec 13 '16 at 11:23
If I understand your remark correctly, I agree on the fact that you should avoid the situation where you will have to compare a list with that many elements. This problem is most likely the consequence of a conception issue. Regarding the strings comparison, there're good api about this like StringUtils (https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html#compareIgnoreCase-java.lang.String-java.lang.String-) — Mickael, Dec 13 '16 at 11:31

How to check Strings equality which are in Uppercase and Lower Case using List Contains Method

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