From fe53a23d41bb69d36f2ea5e7885d214b461cbd81 Mon Sep 17 00:00:00 2001
From: Anurag Goyal <anurag.alw@gmail.com>
Date: Sun, 7 Apr 2019 16:48:07 +0530
Subject: [PATCH] updated post review comments

---
 .../filechannel/FileChannelUnitTest.java      | 288 ++++++++++--------
 1 file changed, 156 insertions(+), 132 deletions(-)

diff --git a/core-java-io/src/test/java/com/baeldung/filechannel/FileChannelUnitTest.java b/core-java-io/src/test/java/com/baeldung/filechannel/FileChannelUnitTest.java
index 35ba9aca65..37b203241b 100644
--- a/core-java-io/src/test/java/com/baeldung/filechannel/FileChannelUnitTest.java
+++ b/core-java-io/src/test/java/com/baeldung/filechannel/FileChannelUnitTest.java
@@ -1,6 +1,7 @@
 package com.baeldung.filechannel;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 
 import java.io.ByteArrayOutputStream;
 import java.io.FileInputStream;
@@ -8,171 +9,194 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.RandomAccessFile;
 import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
 import java.nio.channels.FileChannel;
+import java.nio.channels.FileLock;
+import java.nio.channels.OverlappingFileLockException;
 import java.nio.charset.StandardCharsets;
 
 import org.junit.Test;
 
 public class FileChannelUnitTest {
-    @Test
-    public void givenFile_whenReadWithFileChannelUsingRandomAccessFile_thenCorrect() throws IOException {
-        String expected_value = "Hello world";
-        String file = "src/test/resources/test_read.in";
-        RandomAccessFile reader = new RandomAccessFile(file, "r");
-        FileChannel channel = reader.getChannel();
-        ByteArrayOutputStream out = new ByteArrayOutputStream();
 
-        int bufferSize = 1024;
-        if (bufferSize > channel.size()) {
-            bufferSize = (int) channel.size();
-        }
-        ByteBuffer buff = ByteBuffer.allocate(bufferSize);
+	@Test
+	public void givenFile_whenReadWithFileChannelUsingRandomAccessFile_thenCorrect() throws IOException {
+		String expected_value = "Hello world";
+		String file = "src/test/resources/test_read.in";
+		
+		try (RandomAccessFile reader = new RandomAccessFile(file, "r");
+				FileChannel channel = reader.getChannel();
+				ByteArrayOutputStream out = new ByteArrayOutputStream();) {
 
-        while (channel.read(buff) > 0) {
-            if (buff.hasArray()) {
-                out.write(buff.array(), 0, buff.position());
-                buff.clear();
-            }
-        }
+			int bufferSize = 1024;
+			if (bufferSize > channel.size()) {
+				bufferSize = (int) channel.size();
+			}
+			ByteBuffer buff = ByteBuffer.allocate(bufferSize);
 
-        assertEquals(expected_value, new String(out.toByteArray(), StandardCharsets.UTF_8));
-        out.close();
-        channel.close();
-        reader.close();
-    }
+			while (channel.read(buff) > 0) {
+				if (buff.hasArray()) {
+					out.write(buff.array(), 0, buff.position());
+					buff.clear();
+				}
+			}
 
-    @Test
-    public void givenFile_whenReadWithFileChannelUsingFileInputStream_thenCorrect() throws IOException {
-        String expected_value = "Hello world";
-        String file = "src/test/resources/test_read.in";
-        ByteArrayOutputStream out = new ByteArrayOutputStream();
-        FileInputStream fin = new FileInputStream(file);
-        FileChannel channel = fin.getChannel();
+			assertEquals(expected_value, new String(out.toByteArray(), StandardCharsets.UTF_8));
+		}
+	}
 
-        int bufferSize = 1024;
-        if (bufferSize > channel.size()) {
-            bufferSize = (int) channel.size();
-        }
-        ByteBuffer buff = ByteBuffer.allocate(bufferSize);
+	
+	@Test
+	public void givenFile_whenReadWithFileChannelUsingFileInputStream_thenCorrect() throws IOException {
+		String expected_value = "Hello world";
+		String file = "src/test/resources/test_read.in";
 
-        while (channel.read(buff) > 0) {
-            if (buff.hasArray()) {
-                out.write(buff.array(), 0, buff.position());
-                buff.clear();
-            }
-        }
+		try (ByteArrayOutputStream out = new ByteArrayOutputStream();
+			FileInputStream fin = new FileInputStream(file);
+			FileChannel channel = fin.getChannel();) {
 
-        assertEquals(expected_value, new String(out.toByteArray(), StandardCharsets.UTF_8));
-        out.close();
-        channel.close();
-        fin.close();
-    }
+			int bufferSize = 1024;
+			if (bufferSize > channel.size()) {
+				bufferSize = (int) channel.size();
+			}
+			ByteBuffer buff = ByteBuffer.allocate(bufferSize);
 
-    @Test
-    public void whenWriteWithFileChannelUsingRandomAccessFile_thenCorrect() throws IOException {
-        String input = "Hello world";
-        String file = "src/test/resources/test_write_using_filechannel.txt";
+			while (channel.read(buff) > 0) {
+				if (buff.hasArray()) {
+					out.write(buff.array(), 0, buff.position());
+					buff.clear();
+				}
+			}
 
-        RandomAccessFile writer = new RandomAccessFile(file, "rw");
-        FileChannel channel = writer.getChannel();
+			assertEquals(expected_value, new String(out.toByteArray(), StandardCharsets.UTF_8));
 
-        ByteBuffer buff = ByteBuffer.wrap(input.getBytes());
-        while (buff.hasRemaining()) {
-            channel.write(buff);
-        }
-        channel.close();
-        writer.close();
+		}
+	}
+	
+	
+	@Test
+	public void givenFile_whenReadAFileSectionIntoMemoryWithFileChannel_thenCorrect() throws IOException {
+		String expected_value = "world";
+		String file = "src/test/resources/test_read.in";
 
-        // verify
-        RandomAccessFile reader = new RandomAccessFile(file, "r");
-        assertEquals(input, reader.readLine());
-        reader.close();
-    }
+		try (RandomAccessFile reader = new RandomAccessFile(file, "r");
+				FileChannel channel = reader.getChannel();
+				ByteArrayOutputStream out = new ByteArrayOutputStream();) {
 
-    @Test
-    public void whenWriteWithFileChannelUsingFileOutputStream_thenCorrect() throws IOException {
-        String input = "Hello world";
-        String file = "src/test/resources/test_write_using_filechannel.txt";
+			MappedByteBuffer buff = channel.map(FileChannel.MapMode.READ_ONLY, 6, 5);
 
-        FileOutputStream fout = new FileOutputStream(file);
-        FileChannel channel = fout.getChannel();
+			if(buff.hasRemaining()) {
+				byte[] data = new byte[buff.remaining()];
+				buff.get(data);
+				assertEquals(expected_value, new String(data, StandardCharsets.UTF_8));
+			
+			}
+			
+		}
+	}
+	
+	
+	@Test
+	public void whenWriteWithFileChannelUsingRandomAccessFile_thenCorrect()   
+	  throws IOException {    
+	    String expected = "Hello world";    
+	    String file = "src/test/resources/test_write_using_filechannel.txt";   
+	    
+	    try (RandomAccessFile writer = new RandomAccessFile(file, "rw");    
+	        FileChannel channel = writer.getChannel();){    
+	        ByteBuffer buff = ByteBuffer.wrap("Hello world".getBytes(StandardCharsets.UTF_8));    
+	        
+	        if (buff.hasRemaining()) {         
+	           channel.write(buff);    
+	        }    
+	             
+	        // verify    
+	        RandomAccessFile reader = new RandomAccessFile(file, "r");    
+	        assertEquals(expected, reader.readLine());    
+	        reader.close();
+	    }
+	}
+	
+	
+	@Test
+	public void givenFile_whenWriteAFileUsingLockAFileSectionWithFileChannel_thenCorrect() throws IOException {
+		String file = "src/test/resources/test_read.in";
 
-        ByteBuffer buff = ByteBuffer.wrap(input.getBytes());
-        while (buff.hasRemaining()) {
-            channel.write(buff);
-        }
+		try (RandomAccessFile reader = new RandomAccessFile(file, "rw");
+		    FileChannel channel = reader.getChannel();
+			FileLock fileLock = channel.tryLock(6, 5, Boolean.FALSE );){
+		
+				 
+		    assertNotNull(fileLock);
+			
+		}catch(OverlappingFileLockException | IOException ex) {
+			
+			
+		}
+	
+	}
+	
 
-        channel.close();
-        fout.close();
+	@Test
+	public void givenFile_whenReadWithFileChannelGetPosition_thenCorrect() throws IOException {
+		long expected_value = 11;
+		String file = "src/test/resources/test_read.in";
 
-        // verify
-        RandomAccessFile reader = new RandomAccessFile(file, "r");
-        assertEquals(input, reader.readLine());
-        reader.close();
-    }
+		try (ByteArrayOutputStream out = new ByteArrayOutputStream();
+			RandomAccessFile reader = new RandomAccessFile(file, "r");
+			FileChannel channel = reader.getChannel();) {
 
-    @Test
-    public void givenFile_whenReadWithFileChannelGetPosition_thenCorrect() throws IOException {
-        long expected_value = 11;
-        String file = "src/test/resources/test_read.in";
-        ByteArrayOutputStream out = new ByteArrayOutputStream();
-        RandomAccessFile reader = new RandomAccessFile(file, "r");
-        FileChannel channel = reader.getChannel();
+			int bufferSize = 1024;
+			if (bufferSize > channel.size()) {
+				bufferSize = (int) channel.size();
+			}
+			ByteBuffer buff = ByteBuffer.allocate(bufferSize);
 
-        int bufferSize = 1024;
-        if (bufferSize > channel.size()) {
-            bufferSize = (int) channel.size();
-        }
-        ByteBuffer buff = ByteBuffer.allocate(bufferSize);
+			while (channel.read(buff) > 0) {
+				out.write(buff.array(), 0, buff.position());
+				buff.clear();
+			}
 
-        while (channel.read(buff) > 0) {
-            if (buff.hasArray()) {
-                out.write(buff.array(), 0, buff.position());
-                buff.clear();
-            }
-        }
+			assertEquals(expected_value, channel.position());
 
-        assertEquals(expected_value, channel.position());
+			channel.position(4);
+			assertEquals(4, channel.position());
 
-        channel.position(4);
-        assertEquals(4, channel.position());
+		}
+	}
 
-        out.close();
-        channel.close();
-        reader.close();
-    }
+	
+	@Test
+	public void whenGetFileSize_thenCorrect() throws IOException {
+		long expectedSize = 11;
+		String file = "src/test/resources/test_read.in";
+		
+		try (RandomAccessFile reader = new RandomAccessFile(file, "r"); 
+			FileChannel channel = reader.getChannel();) {
 
-    @Test
-    public void whenGetFileSize_thenCorrect() throws IOException {
-        long expectedSize = 11;
-        String file = "src/test/resources/test_read.in";
-        RandomAccessFile reader = new RandomAccessFile(file, "r");
-        FileChannel channel = reader.getChannel();
+			long imageFileSize = channel.size();
+			assertEquals(expectedSize, imageFileSize);
+		}
 
-        long imageFileSize = channel.size();
-        assertEquals(expectedSize, imageFileSize);
+	}
 
-        channel.close();
-        reader.close();
-    }
+	@Test
+	public void whenTruncateFile_thenCorrect() throws IOException {
+		long expectedSize = 5;
+		String input = "this is a test input";
+		String file = "src/test/resources/test_truncate.txt";
 
-    @Test
-    public void whenTruncateFile_thenCorrect() throws IOException {
-        long expectedSize = 5;
-        String input = "this is a test input";
-        String file = "src/test/resources/test_truncate.txt";
+		FileOutputStream fout = new FileOutputStream(file);
+		FileChannel channel = fout.getChannel();
 
-        FileOutputStream fout = new FileOutputStream(file);
-        FileChannel channel = fout.getChannel();
+		ByteBuffer buff = ByteBuffer.wrap(input.getBytes());
+		channel.write(buff);
+		buff.flip();
 
-        ByteBuffer buff = ByteBuffer.wrap(input.getBytes());
-        channel.write(buff);
-        buff.flip();
+		channel = channel.truncate(5);
+		assertEquals(expectedSize, channel.size());
 
-        channel = channel.truncate(5);
-        assertEquals(expectedSize, channel.size());
-
-        fout.close();
-        channel.close();
-    }
+		fout.close();
+		channel.close();
+	}
 }