What is the @TempDir annotation in JUnit 6?

import org.junit.jupiter.api.io.TempDir;
import java.nio.file.Path;
import java.io.File;

class TempDirTest {

    // Method parameter injection: per-test temp directory
    @Test
    void writesAndReadsFile(@TempDir Path tempDir) throws Exception {
        Path file = tempDir.resolve("report.txt");
        Files.writeString(file, "Test output");
        assertEquals("Test output", Files.readString(file));
        // Directory is automatically deleted after the test
    }

    // Field injection: same directory reused across tests in class
    @TempDir
    static Path sharedTempDir;  // static = shared across all tests

    @Test
    void firstTestUsesSharedDir() throws Exception {
        Files.writeString(sharedTempDir.resolve("a.txt"), "hello");
    }

    @Test
    void secondTestSeesFilesFromFirst() throws Exception {
        // sharedTempDir persists between tests (static)
        assertTrue(Files.exists(sharedTempDir.resolve("a.txt")));
    }

    // Can also inject as java.io.File:
    @Test
    void withFileType(@TempDir File tempDir) {
        File output = new File(tempDir, "result.csv");
        // ... file operations
    }
}