add code

.classpath

+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" output="bin/main" path="src/main/java">
+		<attributes>
+			<attribute name="gradle_scope" value="main"/>
+			<attribute name="gradle_used_by_scope" value="main,test"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" output="bin/test" path="src/test/java">
+		<attributes>
+			<attribute name="gradle_scope" value="test"/>
+			<attribute name="gradle_used_by_scope" value="test"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8/"/>
+	<classpathentry kind="con" path="org.eclipse.buildship.core.gradleclasspathcontainer"/>
+	<classpathentry kind="output" path="bin/default"/>
+</classpath>

.gitignore

@@ -3,3 +3,5 @@
 
 # Ignore Gradle build output directory
 build/
+
+*.db
\ No newline at end of file

.project

+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>csubuapp</name>
+	<comment>Project gradle-project created by Buildship.</comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.buildship.core.gradleprojectbuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+		<nature>org.eclipse.buildship.core.gradleprojectnature</nature>
+	</natures>
+</projectDescription>

.settings/org.eclipse.buildship.core.prefs

+connection.project.dir=
+eclipse.preferences.version=1

.vscode/settings.json

+{
+    "java.configuration.updateBuildConfiguration": "disabled"
+}
\ No newline at end of file

build.gradle

@@ -34,4 +34,6 @@ dependencies {
 }
 
 // Define the main class for the application
-mainClassName = 'edu.ubu.csapp.App'
+//mainClassName = 'edu.ubu.csapp.App'
+// mainClassName = 'edu.ubu.csapp.DataStreamApp'
+mainClassName = 'edu.ubu.csapp.PointOfSaleApp'

src/main/java/edu/ubu/csapp/DataStreamApp.java

+package edu.ubu.csapp;
+
+import java.io.*;
+import java.util.*;
+
+public class DataStreamApp {
+
+  static Product[] products = {
+      new Product("Shirt", 250.00, 10),
+      new Product("Jeans", 1550.00, 15),
+      new Product("Mug", 150.00, 20),
+      new Product("Jacket", 5499.00, 5),
+      new Product("Computer", 26490.00, 8)
+  };
+
+  static void save(String fileName) {
+      try (DataOutputStream out = new DataOutputStream(
+                  new BufferedOutputStream(
+                    new FileOutputStream(fileName)
+                  )
+                 )
+          ) {
+          for (Product p : products) {
+              out.writeUTF(p.getDescription());
+              out.writeDouble(p.getPrice());
+              out.writeInt(p.getUnit());
+          }
+
+      } catch (IOException ex) {
+        ex.printStackTrace();
+      }
+  }
+
+  static ArrayList<Product> load(String fileName) {
+      ArrayList<Product> productList = new ArrayList<Product>();
+      try (DataInputStream input = new DataInputStream(
+                    new BufferedInputStream(
+                      new FileInputStream(fileName)
+                    )
+                  )
+              ) {
+          while (true) {
+              Product p = new Product();
+              p.setDescription(input.readUTF());
+              p.setPrice(input.readDouble());
+              p.setUnit(input.readInt());
+              System.out.println(p);
+              productList.add(p);
+          }
+      } catch (EOFException e) {
+        e.printStackTrace();
+      } catch (IOException e) {
+        e.printStackTrace();
+      }
+    return productList;
+  }
+
+  public static void main(String[] args) throws IOException {
+    save(args[1]);
+    ArrayList<Product> productList = load(args[1]);
+  }
+}
\ No newline at end of file

src/main/java/edu/ubu/csapp/ObjectStreamApp.java

+package edu.ubu.csapp;
+
+import java.io.*;
+
+public class ObjectStreamApp {
+
+  static Product[] products = {
+      new Product("Shirt", 250.00, 10),
+      new Product("Jeans", 1550.00, 15),
+      new Product("Mug", 150.00, 20),
+      new Product("Jacket", 5499.00, 5),
+      new Product("Computer", 26490.00, 8)
+  };
+
+  static void saveObject(String fileName) {
+      try (ObjectOutputStream out = new ObjectOutputStream(
+                  new BufferedOutputStream(
+                    new FileOutputStream(fileName)
+                  )
+                 )
+          ) {
+          out.writeObject(products);
+      } catch (IOException ex) {
+        ex.printStackTrace();
+      }
+  }
+
+  static Product[] loadObject(String fileName) {
+      Product[] products = null;
+      try (ObjectInputStream input = new ObjectInputStream(
+                    new BufferedInputStream(
+                      new FileInputStream(fileName)
+                    )
+               )
+             ) {
+          products = (Product[])(input.readObject());
+      } catch (ClassNotFoundException e) {
+        e.printStackTrace();
+      } catch (EOFException e) {
+        e.printStackTrace();
+      } catch (IOException e) {
+        e.printStackTrace();
+      }
+    return products;
+  }
+
+  public static void main(String[] args) throws IOException {
+    saveObject(args[1]);
+    Product[] products = loadObject(args[1]);
+  }
+
+}
\ No newline at end of file

src/main/java/edu/ubu/csapp/PointOfSaleApp.java

+package edu.ubu.csapp;
+
+import java.util.Scanner;
+
+public class PointOfSaleApp {
+
+    // java -cp build/libs/csubuapp.jar edu.ubu.csapp.PointOfSaleApp
+    public static void main(String[] args) {
+        Scanner s = new Scanner(System.in);
+        System.out.print("ระบุจำนวนสินค้า: ");
+        int n = s.nextInt();
+        s.nextLine();
+
+        for (int i=0; i<n; i++) {
+            System.out.printf("ชื่อสินค้า #%d: ", i+1);
+            String desc = s.nextLine();
+            System.out.printf("ราคาสินค้า #%d: ", i+1);
+            double price = s.nextDouble();
+            System.out.printf("จำนวนชิ้นของสินค้า #%d: ", i+1);
+            int unit = s.nextInt();
+            s.nextLine();
+        }
+    }
+
+}
\ No newline at end of file

src/main/java/edu/ubu/csapp/Product.java

+package edu.ubu.csapp;
+
+import java.io.Serializable;
+
+public class Product implements Serializable {
+
+  private static final long serialVersionUID = 1234567L;
+
+  private String description;
+  private double price;
+  private int    unit;
+
+  public Product() {
+  }
+
+  public Product(String description, double price, int unit) {
+    this.description = description;
+    this.price = price;
+    this.unit = unit;
+  }
+
+  public String getDescription() { return description; }
+  public double getPrice() { return price; }
+  public int getUnit() { return unit; }
+
+  public void setDescription(String description) { this.description = description; }
+  public void setPrice(double price) { this.price = price; }
+  public void setUnit(int unit) { this.unit = unit; }
+
+  @Override
+  public String toString() {
+    return String.format("สั่งสินค้า '%s' จำนวน %d ชิ้น ราคาชิ้นละ %.2f บาท", description, unit, price);
+  }
+}
\ No newline at end of file