Master Elegant Null Checks in Java with StringUtils and ObjectUtils

Null pointer exceptions are common bugs; developers often add a != null check, but frequent checks can be cumbersome.

This article shows how to perform null checks efficiently and elegantly using appropriate utility classes.

Step 1 : Identify the data type (String, Object, List, Array, Map, etc.).

Step 2 : Choose the corresponding utility class: StringUtils for strings, ObjectUtils for objects, Arrays for arrays, Collections/CollectionUtils for collections.

Step 3 : Use the utility class to perform the check.

For String:

String str = "";
StringUtils.isEmpty(str); // true

Implementation of StringUtils.isEmpty:

public static boolean isEmpty(@Nullable Object str) {
    return str == null || "".equals(str);
}

For Object, Map, List, and Array you can use ObjectUtils.isEmpty:

Object obj = null;
ObjectUtils.isEmpty(obj); // true

Map<String,Object> map = Collections.emptyMap();
ObjectUtils.isEmpty(map); // true

List<Integer> list = Collections.EMPTY_LIST;
ObjectUtils.isEmpty(list); // true

Object[] objArr = null;
ObjectUtils.isEmpty(objArr); // true

The ObjectUtils.isEmpty method handles many types by checking for null, Optional, CharSequence, arrays, Collections, and Maps.

public static boolean isEmpty(@Nullable Object obj) {
    if (obj == null) return true;
    if (obj instanceof Optional) return !((Optional) obj).isPresent();
    if (obj instanceof CharSequence) return ((CharSequence) obj).length() == 0;
    if (obj.getClass().isArray()) return Array.getLength(obj) == 0;
    if (obj instanceof Collection) return ((Collection) obj).isEmpty();
    if (obj instanceof Map) return ((Map) obj).isEmpty();
    return false;
}

Note: ObjectUtils.isEmpty does not detect null elements inside collections or arrays. For such cases, iterate or use Streams:

Arrays.stream(list.toArray()).allMatch(ObjectUtils::isEmpty);

For Map emptiness, CollectionUtils.isEmpty provides a concise check:

Map<String,Object> map = Collections.emptyMap();
CollectionUtils.isEmpty(map);

Similarly, CollectionUtils.isEmpty works for lists:

List<Integer> list = null;
CollectionUtils.isEmpty(list); // true

Summary : Determine the data type, select the appropriate utility class, and use its isEmpty method. Use StringUtils for strings; ObjectUtils for other types; and CollectionUtils for collections when needed. For nested null checks, iterate over elements.