Guava in Java

Guava in Java

What is Guava?

Guava is an open-source Java library developed by Google. It provides a wide variety of core libraries that complement Java’s standard libraries. Guava focuses on making Java programming easier, safer, and more efficient.

Some key areas Guava helps with:

  1. Collections
  2. Caching
  3. Functional programming utilities
  4. String manipulation
  5. Concurrency utilities
  6. Hashing
  7. I/O utilities

1. Collections

Guava provides advanced collection types and utilities that Java doesn’t natively have.

Examples:

  • Immutable collections
import com.google.common.collect.ImmutableList;

ImmutableList<String> list = ImmutableList.of("apple", "banana", "guava");

Immutable collections cannot be modified after creation, which helps prevent bugs.

  • Multimap (a map that allows multiple values per key)
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;

Multimap<String, String> multimap = ArrayListMultimap.create();
multimap.put("fruit", "apple");
multimap.put("fruit", "banana");
System.out.println(multimap.get("fruit")); // [apple, banana]
  • BiMap (a bidirectional map)
import com.google.common.collect.HashBiMap;
import com.google.common.collect.BiMap;

BiMap<Integer, String> userMap = HashBiMap.create();
userMap.put(1, "Alice");
userMap.put(2, "Bob");
System.out.println(userMap.inverse().get("Alice")); // 1

2. Caching

Guava provides an in-memory cache mechanism that’s thread-safe and easy to use.

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;

Cache<String, Integer> cache = CacheBuilder.newBuilder()
    .maximumSize(100)
    .build();

cache.put("apple", 10);
System.out.println(cache.getIfPresent("apple")); // 10

3. Functional Programming Utilities

Guava includes utilities like Optional, which represents a value that may or may not be present.

import com.google.common.base.Optional;

Optional<String> name = Optional.of("Guava");
System.out.println(name.isPresent()); // true
System.out.println(name.get());       // Guava

4. String Utilities

Guava provides helper methods for string manipulation.

import com.google.common.base.Joiner;
import com.google.common.base.Splitter;

String joined = Joiner.on(", ").join("apple", "banana", "guava");
System.out.println(joined); // apple, banana, guava

Iterable<String> parts = Splitter.on(", ").split("apple, banana, guava");
parts.forEach(System.out::println);

5. Hashing

Guava has powerful hashing utilities.

import com.google.common.hash.Hashing;
import java.nio.charset.StandardCharsets;

int hash = Hashing.murmur3_32().hashString("Guava", StandardCharsets.UTF_8).asInt();
System.out.println(hash);

6. Why Use Guava?

  • Cleaner and safer code.
  • Reduces boilerplate.
  • Adds useful collection types and utilities not in Java standard library.
  • Highly optimized and maintained by Google.

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