isclaimer: This is not an official Google product.

Mug ()

A small Java 8+ string processing and streams library (javadoc), widely used in Google’s internal Java codebase, with 0 deps (Proto, BigQuery, Guava addons are in separate artifacts).

Full Spectrum of String Utilities

✅ Substring – simple and composable substring extraction & manipulation
→ Substring.between("(", ")").from("call(foo)") → "foo"
✅ StringFormat – compile-time-safe bidirectional parsing/formatting
→ new StringFormat("/home/{user}/{date}").parse(filePath, (user, date) -> ...)

✅ Parser – everyday string parsing easier than and beyond regex

sequence(word().followedBy("="), digits(), Map::entry)
    .zeroOrMoreDelimitedBy(",")
    .between("{", "}")         // {k1=100, k2=200, k3=300, ...}
    .parse(input);

DateTimeFormats – define datetime formats by examples
→ DateTimeFormatter format = formatOf("2024-03-14 10.20:00.123 America/New_York")

Streams

✅ BiStream – streams Map and pair-wise collections
→ BiStream.zip(keys, values).toMap()

✅ MoreStreams – extra stream utilities

Stream<List<Double>> greenDays = MoreStreams.groupConsecutive(
    stockPrices, (p1, p2) -> p1 <= p2, toUnmodifiableList());

Others

✅ @ParametersMustMatchByNamerecord Profile(String userId, String userName) {}
- new Profile(user.id(), user.name()) Compiles ✅
- new Profile(user.name(), user.id()) Does Not Compile ❌
✅ SafeSql – compile-time-enforced safe, composable SQL template
→ SafeSql.of("select id, `{col}` from Users where id = {id}", col, id)

More tools

Iteration - implement lazy stream with recursive code
BinarySearch - solve LeetCode binary search problems
→ BinarySearch.inSortedArrayWithTolerance(doubleArray, 0.0001).find(target)
StructuredConcurrency - simple structured concurrency on virtual threads
→ concurrently(() -> fetchArm(), () -> fetchLeg(), (arm, leg) -> makeRobot(arm, leg))
Optionals
→ return optionally(obj.hasFoo(), obj::getFoo);

Installation

Maven

Add the following to pom.xml:

  <dependency>
    <groupId>com.google.mug</groupId>
    <artifactId>mug</artifactId>
    <version>10.2</version>
  </dependency>

Add mug-errorprone to your annotationProcessorPaths:

  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <configuration>
            <annotationProcessorPaths>
              <path>
                <groupId>com.google.errorprone</groupId>
                <artifactId>error_prone_core</artifactId>
                <version>2.23.0</version>
              </path>
              <path>
                <groupId>com.google.mug</groupId>
                <artifactId>mug-errorprone</artifactId>
                <version>10.2</version>
              </path>
            </annotationProcessorPaths>
          </configuration>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>

SafeSql (javadoc):

  <dependency>
    <groupId>com.google.mug</groupId>
    <artifactId>mug-safesql</artifactId>
    <version>10.2</version>
  </dependency>

Dot Parse Combinators (javadoc):

  <dependency>
    <groupId>com.google.mug</groupId>
    <artifactId>dot-parse</artifactId>
    <version>10.2</version>
  </dependency>

Protobuf utils (javadoc):

  <dependency>
    <groupId>com.google.mug</groupId>
    <artifactId>mug-protobuf</artifactId>
    <version>10.2</version>
  </dependency>

Gradle

Add to build.gradle:

  implementation 'com.google.mug:mug:10.2'
  implementation 'com.google.mug:mug-safesql:10.2'
  implementation 'com.google.mug:dot-parse:10.2'
  implementation 'com.google.mug:mug-guava:10.2'
  implementation 'com.google.mug:mug-protobuf:10.2'