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core-java-modules/core-java-nio-2/src/test/java/com/baeldung/lock/FileLocksTest.java

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+package com.baeldung.lock;
+
+import static org.junit.Assert.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+import java.nio.channels.FileLock;
+import java.nio.channels.NonReadableChannelException;
+import java.nio.channels.NonWritableChannelException;
+
+import org.junit.jupiter.api.Test;
+
+class FileLocksTest {
+
+	// Exclusive locks
+	/**
+	 * Getting an exclusive (write) lock on the entire file.
+	 * Fails when getting the lock from a FileChannel obtained through a FileInputStream.
+	 */
+	@Test
+	void givenAnInputStream_whenGetWriteLock_throwNonWritableChannelException() {
+		assertThrows(NonWritableChannelException.class, 
+				() -> FileLocks.getExclusiveLockFromInputStream());
+	}
+	
+	/**
+	 * Getting and exclusive lock from a RandomAccessFile
+	 * @throws IOException
+	 */
+	@Test
+	void givenARandomAccessFileWithReadWriteAccess_whenGetWriteLock_lock() throws IOException {
+		FileLock lock = FileLocks.getExclusiveLockFromRandomAccessFile(0, 10);
+		assertNotNull(lock);
+		assertFalse(lock.isShared());
+	}
+	
+	/**
+	 * Getting an exclusive lock from FileChannel::open
+	 * @throws IOException
+	 */
+	@Test
+	void givenAPath_whenGetExclusiveLock_lock() throws IOException {
+		FileLock lock = FileLocks.getExclusiveLockFromFileChannelOpen(0, 10);
+		assertNotNull(lock);
+		assertFalse(lock.isShared());
+	}
+	
+	
+	/**
+	 * Getting a shared (read) lock works fine when getting the lock from a FileChannel obtained through a FileInputStream.
+	 * @throws IOException
+	 */
+	@Test
+	void givenAnInputStream_whenGetSharedLock_lock() throws IOException {
+		FileLock lock = FileLocks.getReadLockFromInputStream(0, 10);
+		assertNotNull(lock);
+		assertTrue(lock.isShared());
+		
+	}
+	
+	
+	@Test
+	void givenAFileOutputStream_whenGetSharedLock_throwNonReadableChannelException() {
+		assertThrows(NonReadableChannelException.class, 
+				() -> FileLocks.getReadLockFromOutputStream(0, 10));
+	}
+	
+	@Test
+	void givenARandomAccessFile_whenGetSharedLock_lock() throws IOException {
+		FileLock lock = FileLocks.getReadLockFromRandomAccessFile(0,  10);
+		assertNotNull(lock);
+		assertTrue(lock.isShared());
+		
+	}
+
+}