add Rule9

yi-yun · yi-yun · commit 6a668131c6f1 · 2019-06-20T14:16:02.000+08:00
diff --git a/effective_java/src/main/java/com/yiyun/Rule09/TestFile.java b/effective_java/src/main/java/com/yiyun/Rule09/TestFile.java
@@ -0,0 +1,42 @@
+package com.yiyun.Rule09;
+
+import java.io.*;
+
+public class TestFile implements AutoCloseable {
+    static String firstLineOfFile(String path) throws IOException {
+        BufferedReader br = new BufferedReader(new FileReader(path));
+        try {
+            return br.readLine();
+        } finally {
+            br.close();
+        }
+    }
+
+    static void copy(String src, String dst) throws IOException {
+        InputStream in = new FileInputStream(src);
+        try {
+            OutputStream out = new FileOutputStream(dst);
+            try {
+                byte[] buf = new byte[1024];
+                int n;
+                while ((n = in.read(buf)) >= 0)
+                    out.write(buf, 0, n);
+            } finally {
+                out.close();
+            }
+        } finally {
+            in.close();
+        }
+    }
+
+    static String firstLineOfFile1(String path) throws IOException {
+        try (BufferedReader br = new BufferedReader(new FileReader(path))) {
+            return br.readLine();
+        }
+    }
+
+    @Override
+    public void close() throws Exception {
+        
+    }
+}
