[add] add some examples of nio

brianway · brianway · commit 490a25fee0a7 · 2016-11-29T17:02:15.000+08:00
diff --git a/java-io/src/main/java/com/brianway/learning/java/nio/BufferToText.java b/java-io/src/main/java/com/brianway/learning/java/nio/BufferToText.java
diff --git a/java-io/src/main/java/com/brianway/learning/java/nio/ChannelCopy.java b/java-io/src/main/java/com/brianway/learning/java/nio/ChannelCopy.java
@@ -0,0 +1,45 @@
+package com.brianway.learning.java.nio;
+
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+
+/**
+ * Created by brian on 16/11/29.
+ */
+public class ChannelCopy {
+
+    private static final int BSIZE = 1024;
+
+    public static void main(String[] args) throws IOException {
+        String parent = ChannelCopy.class.getResource("/").getPath();
+        String infile = parent + "/infile.txt";
+        String outCopy = parent + "/outCopy.txt";
+        String outTransferTo = parent + "/outTransferTo.txt";
+        copy(infile, outCopy);
+        transferTo(infile, outTransferTo);
+    }
+
+    private static void copy(String infile, String outfile) throws IOException {
+        FileChannel
+                in = new FileInputStream(infile).getChannel(),
+                out = new FileOutputStream(outfile).getChannel();
+        ByteBuffer buffer = ByteBuffer.allocate(BSIZE);
+        while (in.read(buffer) != -1) {
+            buffer.flip(); // prepare for writing
+            out.write(buffer);
+            buffer.clear(); // prepare for reading
+        }
+    }
+
+    private static void transferTo(String infile, String outfile) throws IOException {
+        FileChannel
+                in = new FileInputStream(infile).getChannel(),
+                out = new FileOutputStream(outfile).getChannel();
+        in.transferTo(0, in.size(), out);
+        // Or:
+        // out.transferFrom(in,0,in.size());
+    }
+}
diff --git a/java-io/src/main/java/com/brianway/learning/java/nio/Endians.java b/java-io/src/main/java/com/brianway/learning/java/nio/Endians.java
@@ -0,0 +1,36 @@
+package com.brianway.learning.java.nio;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.Arrays;
+
+/**
+ * Created by brian on 16/11/29.
+ *
+ * "big endian"(高位优先),将最重要的字节放在地址最低的存储器单元;
+ * "little endian"(低位优先),将最重要的字节放在地址最高的存储器单元;
+ *
+ * ByteBuffer 是以高位优先的形式存储数据的。
+ */
+public class Endians {
+    public static void main(String[] args) {
+        ByteBuffer bb = ByteBuffer.wrap(new byte[12]);
+        bb.asCharBuffer().put("abcdef");
+        System.out.println(Arrays.toString(bb.array()));
+
+        bb.rewind();
+        bb.order(ByteOrder.BIG_ENDIAN);
+        bb.asCharBuffer().put("abcdef");
+        System.out.println(Arrays.toString(bb.array()));
+
+        bb.rewind();
+        bb.order(ByteOrder.LITTLE_ENDIAN);
+        bb.asCharBuffer().put("abcdef");
+        System.out.println(Arrays.toString(bb.array()));
+    }
+}
+/* Output:
+[0, 97, 0, 98, 0, 99, 0, 100, 0, 101, 0, 102]
+[0, 97, 0, 98, 0, 99, 0, 100, 0, 101, 0, 102]
+[97, 0, 98, 0, 99, 0, 100, 0, 101, 0, 102, 0]
+*///:~
diff --git a/java-io/src/main/java/com/brianway/learning/java/nio/GetChannel.java b/java-io/src/main/java/com/brianway/learning/java/nio/GetChannel.java
@@ -0,0 +1,47 @@
+package com.brianway.learning.java.nio;
+
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+
+/**
+ * Created by brian on 16/11/29.
+ */
+public class GetChannel {
+    private static final int BSIZE = 1024;
+
+    public static void main(String[] args) throws IOException {
+        String parent = GetChannel.class.getResource("/").getPath();
+        String filename = parent + "/data.txt";
+        write(filename);
+        addToEnd(filename);
+        read(filename);
+    }
+
+    private static void write(String filename) throws IOException {
+        FileChannel fc = new FileOutputStream(filename).getChannel();
+        fc.write(ByteBuffer.wrap("Some text ".getBytes()));
+        fc.close();
+    }
+
+    private static void addToEnd(String filename) throws IOException {
+        FileChannel fc = new RandomAccessFile(filename, "rw").getChannel();
+        fc.position(fc.size());
+        fc.write(ByteBuffer.wrap("Some more ".getBytes()));
+        fc.close();
+    }
+
+    private static void read(String filename) throws IOException {
+        FileChannel fc = new FileInputStream(filename).getChannel();
+        ByteBuffer buff = ByteBuffer.allocate(BSIZE);
+        fc.read(buff);
+        buff.flip();
+        while (buff.hasRemaining()) {
+            System.out.print((char) buff.get());
+        }
+        fc.close();
+    }
+}
diff --git a/java-io/src/main/java/com/brianway/learning/java/nio/ViewBuffers.java b/java-io/src/main/java/com/brianway/learning/java/nio/ViewBuffers.java
@@ -0,0 +1,78 @@
+package com.brianway.learning.java.nio;//: io/ViewBuffers.java
+
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.DoubleBuffer;
+import java.nio.FloatBuffer;
+import java.nio.IntBuffer;
+import java.nio.LongBuffer;
+import java.nio.ShortBuffer;
+
+/**
+ * Created by brian on 16/11/29.
+ *
+ * 通过在同一个 ByteBuffer 上建立不同的试图缓冲器,
+ * 将同一字节序列翻译成short,int,float,long,double等类型的数据
+ */
+
+public class ViewBuffers {
+    public static void main(String[] args) {
+        ByteBuffer bb = ByteBuffer.wrap(
+                new byte[] {0, 0, 0, 0, 0, 0, 0, 'a'});
+        bb.rewind();
+        System.out.print("Byte Buffer ");
+        while (bb.hasRemaining())
+            System.out.print(bb.position() + " -> " + bb.get() + ", ");
+        System.out.println();
+
+        CharBuffer cb =
+                ((ByteBuffer) bb.rewind()).asCharBuffer();
+        System.out.println("Char Buffer ");
+        while (cb.hasRemaining())
+            System.out.print(cb.position() + " -> " + cb.get() + ", ");
+        System.out.println();
+
+        FloatBuffer fb =
+                ((ByteBuffer) bb.rewind()).asFloatBuffer();
+        System.out.print("Float Buffer ");
+        while (fb.hasRemaining())
+            System.out.print(fb.position() + " -> " + fb.get() + ", ");
+        System.out.println();
+
+        IntBuffer ib =
+                ((ByteBuffer) bb.rewind()).asIntBuffer();
+        System.out.print("Int Buffer ");
+        while (ib.hasRemaining())
+            System.out.print(ib.position() + " -> " + ib.get() + ", ");
+        System.out.println();
+
+        LongBuffer lb =
+                ((ByteBuffer) bb.rewind()).asLongBuffer();
+        System.out.print("Long Buffer ");
+        while (lb.hasRemaining())
+            System.out.print(lb.position() + " -> " + lb.get() + ", ");
+        System.out.println();
+
+        ShortBuffer sb =
+                ((ByteBuffer) bb.rewind()).asShortBuffer();
+        System.out.print("Short Buffer ");
+        while (sb.hasRemaining())
+            System.out.print(sb.position() + " -> " + sb.get() + ", ");
+        System.out.println();
+
+        DoubleBuffer db =
+                ((ByteBuffer) bb.rewind()).asDoubleBuffer();
+        System.out.print("Double Buffer ");
+        while (db.hasRemaining())
+            System.out.print(db.position() + " -> " + db.get() + ", ");
+    }
+}
+/* Output:
+Byte Buffer 0 -> 0, 1 -> 0, 2 -> 0, 3 -> 0, 4 -> 0, 5 -> 0, 6 -> 0, 7 -> 97,
+Char Buffer 0 ->  , 1 ->  , 2 ->  , 3 -> a,
+Float Buffer 0 -> 0.0, 1 -> 1.36E-43,
+Int Buffer 0 -> 0, 1 -> 97,
+Long Buffer 0 -> 97,
+Short Buffer 0 -> 0, 1 -> 0, 2 -> 0, 3 -> 97,
+Double Buffer 0 -> 4.8E-322,
+*///:~
