added builder example

src/learn/simple_builder/Builder.java

@@ -0,0 +1,16 @@
+package learn.simple_builder;
+
+public abstract class Builder {
+    protected Product product;
+
+    public void setProduct(Product product) {
+        this.product = product;
+    }
+    public Product getProduct() {
+        return product;
+    }
+
+    public abstract void buildPartA();
+    public abstract void buildPartB();
+    public abstract void buildPartC();
+}

src/learn/simple_builder/ConcreteBuilder.java

@@ -0,0 +1,18 @@
+package learn.simple_builder;
+
+public class ConcreteBuilder extends Builder {
+    @Override
+    public void buildPartA() {
+        product.setPartA("material 1");
+    }
+
+    @Override
+    public void buildPartB() {
+        product.setPartB("material 2");
+    }
+
+    @Override
+    public void buildPartC() {
+        product.setPartC("material 3");
+    }
+}

src/learn/simple_builder/Director.java

@@ -0,0 +1,18 @@
+package learn.simple_builder;
+
+public class Director {
+    private Builder builder;
+    private Product product;
+
+    public void setBuilder(Builder builder) {
+        this.builder = builder;
+        product = new Product();
+        this.builder.setProduct(product);
+    }
+
+    public void construct() {
+        builder.buildPartA();
+        builder.buildPartB();
+        builder.buildPartC();
+    }
+}

src/learn/simple_builder/Main.java

@@ -0,0 +1,12 @@
+package learn.simple_builder;
+
+public class Main {
+    public static void main(String[] args) {
+        Builder builder = new ConcreteBuilder();
+        Director director = new Director();
+        director.setBuilder(builder);
+        director.construct();
+        Product finalProduct = builder.getProduct();
+        System.out.println(finalProduct);
+    }
+}

src/learn/simple_builder/Product.java

@@ -0,0 +1,28 @@
+package learn.simple_builder;
+
+public class Product {
+    private String partA;
+    private String partB;
+    private String partC;
+
+    @Override
+    public String toString() {
+        return "Product{" +
+                "partA='" + partA + '\'' +
+                ", partB='" + partB + '\'' +
+                ", partC='" + partC + '\'' +
+                '}';
+    }
+
+    public void setPartA(String partA) {
+        this.partA = partA;
+    }
+
+    public void setPartB(String partB) {
+        this.partB = partB;
+    }
+
+    public void setPartC(String partC) {
+        this.partC = partC;
+    }
+}