Mock-up for Java-based build tool (single source execution)

Build.java

import javax.tools.*;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

public class Build {
  public static void main(String... args) throws Exception {
    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
    List<JavaFileObject> files = new ArrayList<>();
    try (DirectoryStream<Path> stream = Files.newDirectoryStream(Paths.get("./src"), "*")) {
      stream.forEach(path -> {
        if (!path.getFileName().toString().endsWith(".java")) {
          return;
        }
        files.add(new SimpleJavaFileObject(path.toUri(), JavaFileObject.Kind.SOURCE) {
          @Override
          public InputStream openInputStream() throws IOException {
            return Files.newInputStream(path);
          }
          @Override
          public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
            try (InputStream inputStream = Files.newInputStream(path)) {
              return new String(inputStream.readAllBytes(), StandardCharsets.UTF_8);
            }
          }
        });
      });
    }
    DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
    StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, StandardCharsets.UTF_8);
    fileManager.setLocation(StandardLocation.CLASS_OUTPUT, List.of(Files.createDirectories(Paths.get("./build")).toFile()));
    JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, diagnostics, null, null, files);
    boolean success = task.call();
    System.out.println("Compiled: " + success);
  }
}