These 9 Java Utility Libraries Boosted My Development Efficiency by 80%

In Java’s vast ecosystem, there are numerous utility classes that significantly enhance development efficiency. Reimplementing existing functionalities wastes time and often yields inferior results. Below are 9 essential tools I frequently use:

1. Collections (java.util.Collections)

A core class for collection operations:
1.1 Sorting

List<Integer> list = Arrays.asList(2, 1, 3);
Collections.sort(list);       // Ascending
Collections.reverse(list);    // Descending

1.2 Max/Min Values

Integer max = Collections.max(list);
Integer min = Collections.min(list);

1.3 Empty Collections

return Collections.emptyList();  // Instead of returning null

1.4 Immutable Collections

List<Integer> unmodifiable = Collections.unmodifiableList(list);
unmodifiable.add(4);  // Throws UnsupportedOperationException

1.5 Thread-Safe Wrappers

List<Integer> syncList = Collections.synchronizedList(list);

2. CollectionUtils (Apache Commons)

Add dependency:

<dependency>
  <groupId>commons-collections</groupId>
  <artifactId>commons-collections</artifactId>
  <version>3.2.2</version>
</dependency>

2.1 Empty Checks

if(CollectionUtils.isEmpty(list)) { ... }
if(CollectionUtils.isNotEmpty(list)) { ... }

2.2 Set Operations

// Union
Collection<Integer> union = CollectionUtils.union(list1, list2);
// Intersection
Collection<Integer> intersect = CollectionUtils.intersection(list1, list2);
// Complement
Collection<Integer> disjunct = CollectionUtils.disjunction(list1, list2);
// Difference
Collection<Integer> diff = CollectionUtils.subtract(list1, list2);

3. Lists (Guava)

Add dependency:

<dependency>
  <groupId>com.google.guava</groupId>
  <artifactId>guava</artifactId>
  <version>28.2-jre</version>
</dependency>

3.1 Quick Initialization

List<Integer> list = Lists.newArrayList(1, 2, 3);

3.2 Cartesian Product

List<List<Integer>> product = Lists.cartesianProduct(list1, list2);

3.3 Partitioning

List<List<Integer>> chunks = Lists.partition(list, 2);  // [[1,2], 
[3,4], [5]]

3.4 Transformations

List<String> upper = Lists.transform(list, String::toUpperCase);

4. Objects(java.util.Objects)

4.1 Null Checks

if(Objects.isNull(obj)) { ... }
if(Objects.nonNull(obj)) { ... }

4.2 Safe Equality

Objects.equals(a, b);  // Null-safe comparison

5. StringUtils (Apache Commons)

5.1 Empty Checks

StringUtils.isEmpty(str);   // Checks null/""
StringUtils.isBlank(str);   // Checks null/""/"   "

5.2 Splitting

StringUtils.split(str, ",");  // Null-safe

5.3 Numeric Check

StringUtils.isNumeric("123");  // true

6. BeanUtils (Spring Framework)

6.1 Property Copy

BeanUtils.copyProperties(source, target);

7. ReflectionUtils (Spring Framework)

7.1 Method Access

Method method = ReflectionUtils.findMethod(MyClass.class, "methodName");

8. DigestUtils (Apache Commons Codec)

8.1 Hashing

String md5 = DigestUtils.md5Hex("data");
String sha256 = DigestUtils.sha256Hex("data");

9. HttpStatus (Spring/HTTP Client)

Replace custom status codes with:

HttpStatus.OK.value();        // 200
HttpStatus.NOT_FOUND.value(); // 404
HttpStatus.INTERNAL_ERROR;    // 500

Summary

These 9 utility libraries streamline common tasks in Java development—from collection manipulation and string processing to reflection and encryption. By leveraging these battle-tested tools, developers can reduce boilerplate code, avoid pitfalls, and focus on business logic.
Note: Some dependency versions may need updating based on your project requirements.