性能优化练习

public class LinkedListCheck {    private static int BOUND = 26;    private static LinkedList<String> aLinkedList = Lists.newLinkedList();    private static LinkedList<String> bLinkedList = Lists.newLinkedList();
    String[] letterArray = {"a","b","c","d","e","f","g","h","i","j","k","l","m","n"            ,"o","p","q","r","s","t","u","v","w","x","y","z"};
    public LinkedListCheck() {        init(13,15);    }
    private void init(int m, int n) {        aLinkedList.add("a");        aLinkedList.add("b");        aLinkedList.add("x");        aLinkedList.add("y");        aLinkedList.add("z");
        bLinkedList.add("d");        bLinkedList.add("e");        bLinkedList.add("f");        bLinkedList.add("x");        bLinkedList.add("y");        bLinkedList.add("z");//        buildLinked(aLinkedList, m);//        buildLinked(bLinkedList, n);        System.out.println(aLinkedList.toString());        System.out.println(bLinkedList.toString());    }
    private void buildLinked(LinkedList<String> linkedList, int size) {        for (int i = 0; i < size; i++) {            Random random = new Random();            int index = random.nextInt(BOUND);            linkedList.add(letterArray[index]);        }    }
    private String findItem() {        int m = aLinkedList.size();        int n = bLinkedList.size();        Map<String, Integer> resultMapA = Maps.newHashMap();        Map<String, Integer> resultMapB = Maps.newHashMap();        for (int i = 0; i < m || i < n; i++) {            String a = null;            if (i<m) {                a = aLinkedList.get(i);            }            String b = null;            if (i<n) {                b = bLinkedList.get(i);            }            String resultA = null;            if (StringUtils.isNotBlank(a)) {                resultA = processMap(resultMapA, resultMapB, a);            }            if(resultA!=null) {                return resultA;            } else {                String resultB = null;                if (StringUtils.isNotBlank(b)) {                    resultB = processMap(resultMapB, resultMapA, b);                }                if(resultB!=null) {                    return resultB;                }            }        }        return null;    }
    private String processMap(Map<String, Integer> storeMap, Map<String, Integer> targetMap,                              String targetValue) {        Integer value = targetMap.getOrDefault(targetValue, 0);        if (value.intValue()>=1) {            return targetValue;        } else {            Integer tempValue = storeMap.getOrDefault(targetValue, 0);            storeMap.put(targetValue, ++tempValue);        }        return null;    }
    public static void main(String[] args) {        LinkedListCheck linkedListCheck = new LinkedListCheck();        System.out.println("合并元素是："+linkedListCheck.findItem());    }}

时间复杂度：O(n)[a, b, x, y, z][d, e, f, x, y, z]合并元素是：x