[Internship] Binary Input Example

java/com/engflow/binaryinput/BUILD

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+load("@rules_java//java:defs.bzl", "java_binary", "java_library")
+
+NUM_FILES = 100
+
+# Generates a number of java files based on the value of NUM_FILES
+# Each file is named HelloX.java where X is the number of the file
+# Each file contains a class with a greetNum method that prints "Hello" + the number of the file
+[genrule(
+    name = "Hello" + str(x),
+    outs = ["Hello" + str(x) + ".java"],
+    cmd_bash = "echo 'package com.engflow.binaryinput;" + "\n" +
+    "public class Hello" + str(x) +
+    " { public static void greetNum() { System.out.println(\"Hello " + str(x) + "\"); } }' > $@",
+) for x in range(1,NUM_FILES+1)]
+
+# Generates a java library that contains all the generated java files
+[java_library(
+    name = "genbinary" + str(x),
+    srcs = [":Hello" + str(x) + ".java" for x in range(1,NUM_FILES+1)],
+    visibility = ["//visibility:public"],
+) for x in range(1,NUM_FILES+1)]
+
+# Main class
+java_binary(
+    name = "main",
+    srcs = ["Main.java"],
+    main_class = "com.engflow.binaryinput.Main",
+    deps = [
+        ":genbinary" + str(x) for x in range(1,NUM_FILES+1)
+    ],
+    args = [str(NUM_FILES)],
+)

java/com/engflow/binaryinput/Main.java

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+package com.engflow.binaryinput;
+
+import java.lang.reflect.InvocationTargetException;
+
+public class Main {
+    public static void main(String[] args) {
+        try {
+            // args[0] is the number of files to read
+            int numFiles = Integer.parseInt(args[0]);
+
+            // Load and run the greetNum method from each class
+            for(int i = 1; i <= numFiles; i++){
+                Class<?> clazz = Class.forName("com.engflow.binaryinput.Hello" + i);
+                clazz.getMethod("greetNum").invoke(null);
+            }
+
+        } catch (ClassNotFoundException | InvocationTargetException | IllegalAccessException | NoSuchMethodException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}

java/com/engflow/binaryinput/README.md

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+# Multiple Binary Input Example
+
+## Usage
+Set the `NUM_FILES` variable in the BUILD file to the desired input size.
+
+To generate the test files, build the `genbinary` library using the `genrule`:
+```sh
+bazel build //java/com/engflow/binaryinput:genbinary{1..<NUM_FILES>}
+```
+
+Then, the program can be built with the following command:
+```sh
+bazel build //java/com/engflow/binaryinput:main
+```
+
+## How It Works
+
+1. **Generation of Java Binaries:**
+    - The `genrule` in the `BUILD` file generates a specified number of Java classes (`Hello1.java`, `Hello2.java`, ..., `HelloN.java`).
+    - Each generated class contains a `greetNum` method that prints a unique message.
+    - A java library is created for each file (`Hello1.jar`, `Hello2.jar`, ..., `HelloN.jar`).
+
+2. **Building the main target:**
+   - The previously created libraries are added to the main class as dependencies through a for loop.
+   - The consistent naming scheme of the libraries simplifies their inclusion in the build process.
+
+3. **Main Class Execution:**
+    - The `Main.java` file in `binaryinput` dynamically loads each generated class using reflection.
+    - It then invokes the `greetNum` method of each class, printing the corresponding message.
+
+## Configuration
+
+The number of generated files is controlled by the `NUM_FILES` variable in the `BUILD` file of the `binaryinput` package. Modify this variable to change the number of generated classes and observe the performance impact on Engflow's remote execution and caching service.
+
+## Example
+
+To generate and run the program with 10 input binary files:
+
+1. Set `NUM_FILES` to 10 in `java/com/engflow/binaryinput/BUILD`.
+2. Build the `genbinary` library:
+   ```sh
+   bazel build //java/com/engflow/binaryinput:genbinary{1..10}
+   ```
+3. Build the `main` binary:
+   ```sh
+   bazel build //java/com/engflow/binaryinput:main
+   ```
+
+This will generate 10 Java classes, build the `genbinary` library, and build the `main` binary. Using `bazel run` will also print messages from each generated class.