Disclaimer: 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).

Strings

• ✅ 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, faster 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 10.8.10:00.123 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());

Compile-Time Guardrails

• ✅ @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-enforcedsafe, 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>10.8.1</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>10.8.1</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>

SafeSql (javadoc):

 <dependency>
<groupId>com.google.mug</groupId>
<artifactId>mug-safesql</artifactId>
<version>10.8.1</version>
</dependency>

Dot Parse Combinators (javadoc):

 <dependency>
<groupId>com.google.mug</groupId>
<artifactId>dot-parse</artifactId>
<version>10.8.1</version>
</dependency>

Protobuf utils (javadoc):

 <dependency>
<groupId>com.google.mug</groupId>
<artifactId>mug-protobuf</artifactId>
<version>10.8.1</version>
</dependency>

Gradle

Add to build.gradle:

 implementation 'com.google.mug:mug:10.8.1'
implementation 'com.google.mug:mug-safesql:10.8.1'
implementation 'com.google.mug:dot-parse:10.8.1'
implementation 'com.google.mug:mug-guava:10.8.1'
implementation 'com.google.mug:mug-protobuf:10.8.1'