add ObjectStream and RandomAccess (#203)

* add ObjectStream and RandomAccess

* fixed gradle building

Author: realDuYuanChao

src/main/java/com/examplehub/basics/io/ObjectOutputInputStreamExample.java

@@ -0,0 +1,4 @@
+package com.examplehub.basics.io;
+
+public class ObjectOutputInputStreamExample {
+}

src/main/java/com/examplehub/basics/io/RandomAccessFileExample.java

@@ -0,0 +1,4 @@
+package com.examplehub.basics.io;
+
+public class RandomAccessFileExample {
+}

src/test/java/com/examplehub/basics/io/ObjectOutputInputStreamExampleTest.java

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+package com.examplehub.basics.io;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.*;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class User implements Serializable{
+  //@Serial TODO
+  private static final long serialVersionUID = 100L;
+  private final String username;
+  private final String password;
+  private final int age;
+
+  public User(String username, String password, int age) {
+    this.username = username;
+    this.password = password;
+    this.age = age;
+  }
+
+  @Override
+  public String toString() {
+    return "User{" +
+            "username='" + username + '\'' +
+            ", password='" + password + '\'' +
+            ", age=" + age +
+            '}';
+  }
+}
+class ObjectOutputInputStreamExampleTest {
+  @Test
+  void testWriteRead() throws IOException, ClassNotFoundException {
+
+    User user = new User("root", "112233", 25);
+    String filename = "user.db";
+    try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(filename))) {
+      oos.writeObject(user);
+    }
+    try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(filename))) {
+      User readUser = (User) ois.readObject();
+      assertEquals(user.toString(), readUser.toString());
+    }
+    assertTrue(Files.deleteIfExists(Paths.get(filename)));
+  }
+}

src/test/java/com/examplehub/basics/io/RandomAccessFileExampleTest.java

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+package com.examplehub.basics.io;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.io.RandomAccessFile;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class RandomAccessFileExampleTest {
+  @Test
+  void testSeek() throws IOException {
+    String filename = "example.txt";
+    try(PrintStream printStream = new PrintStream(new FileOutputStream(filename));
+        RandomAccessFile randomAccessFile = new RandomAccessFile(filename, "rw")) {
+      printStream.write("Java".getBytes(StandardCharsets.UTF_8));
+      printStream.flush();
+
+      assertEquals('J', randomAccessFile.read());
+      randomAccessFile.seek(2);
+      assertEquals('v', randomAccessFile.read());
+      randomAccessFile.write("123".getBytes(StandardCharsets.UTF_8));
+      randomAccessFile.seek(0);
+      assertEquals("Jav123", randomAccessFile.readLine());
+    }
+    assertTrue(Files.deleteIfExists(Paths.get(filename)));
+  }
+}