Complete Example Code for BAEL-782 (#2270)

* added updated example codes

* updated example code StringToCharStream

* deleted StringToCharStream.java locally

* removed redundant file

* added code for apache commons collection SetUtils

* refactored example code

* added example code for bytebuddy

libraries/pom.xml

@@ -530,6 +530,16 @@
             <artifactId>hll</artifactId>
             <version>${hll.version}</version>
         </dependency>
+        <dependency>
+            <groupId>net.bytebuddy</groupId>
+            <artifactId>byte-buddy</artifactId>
+            <version>${bytebuddy.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>net.bytebuddy</groupId>
+            <artifactId>byte-buddy-agent</artifactId>
+            <version>${bytebuddy.version}</version>
+        </dependency>
     </dependencies>
     <properties>
         <multiverse.version>0.7.0</multiverse.version>
@@ -572,6 +582,7 @@
         <vaadin.theme>mytheme</vaadin.theme>
         <!-- /Vaadin -->
         <hll.version>1.6.0</hll.version>
+        <bytebuddy.version>1.7.1</bytebuddy.version>
     </properties>
     <profiles>
         <!-- Vaadin -->

libraries/src/main/java/com/baeldung/bytebuddy/Bar.java

@@ -0,0 +1,16 @@
+package com.baeldung.bytebuddy;
+
+import net.bytebuddy.implementation.bind.annotation.BindingPriority;
+
+public class Bar {
+
+    @BindingPriority(3)
+    public static String sayHelloBar() { return "Holla in Bar!"; }
+
+    @BindingPriority(2)
+    public static String sayBar() { return "bar"; }
+
+    public String bar() { return Bar.class.getSimpleName() + " - Bar"; }
+
+
+}

libraries/src/main/java/com/baeldung/bytebuddy/Foo.java

@@ -0,0 +1,7 @@
+package com.baeldung.bytebuddy;
+
+public class Foo {
+
+    public String sayHelloFoo() { return "Hello in Foo!"; }
+
+}

libraries/src/test/java/com/baeldung/bytebuddy/ByteBuddyUnitTest.java

@@ -0,0 +1,89 @@
+package com.baeldung.bytebuddy;
+
+import net.bytebuddy.ByteBuddy;
+import net.bytebuddy.agent.ByteBuddyAgent;
+import net.bytebuddy.dynamic.DynamicType;
+import net.bytebuddy.dynamic.loading.ClassLoadingStrategy;
+import net.bytebuddy.dynamic.loading.ClassReloadingStrategy;
+import net.bytebuddy.implementation.FixedValue;
+import net.bytebuddy.implementation.MethodDelegation;
+import net.bytebuddy.matcher.ElementMatchers;
+import org.junit.Test;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+
+import static net.bytebuddy.matcher.ElementMatchers.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+public class ByteBuddyUnitTest {
+
+    @Test
+    public void givenObject_whenToString_thenReturnHelloWorldString() throws InstantiationException, IllegalAccessException {
+        DynamicType.Unloaded unloadedType = new ByteBuddy()
+          .subclass(Object.class)
+          .method(ElementMatchers.isToString())
+          .intercept(FixedValue.value("Hello World ByteBuddy!"))
+          .make();
+
+        Class<?> dynamicType = unloadedType.load(getClass().getClassLoader())
+          .getLoaded();
+
+        assertEquals(dynamicType.newInstance().toString(), "Hello World ByteBuddy!");
+    }
+
+    @Test
+    public void givenFoo_whenRedefined_thenReturnFooRedefined() throws Exception {
+        ByteBuddyAgent.install();
+        new ByteBuddy()
+            .redefine(Foo.class)
+            .method(named("sayHelloFoo"))
+            .intercept(FixedValue.value("Hello Foo Redefined"))
+            .make()
+            .load(Foo.class.getClassLoader(), ClassReloadingStrategy.fromInstalledAgent());
+        Foo f = new Foo();
+        assertEquals(f.sayHelloFoo(), "Hello Foo Redefined");
+    }
+
+    @Test
+    public void givenSayHelloFoo_whenMethodDelegation_thenSayHelloBar() throws IllegalAccessException, InstantiationException {
+
+        String r = new ByteBuddy()
+          .subclass(Foo.class)
+          .method(
+            named("sayHelloFoo")
+            .and(isDeclaredBy(Foo.class)
+            .and(returns(String.class)))
+          )
+          .intercept(MethodDelegation.to(Bar.class))
+          .make()
+          .load(getClass().getClassLoader())
+          .getLoaded()
+          .newInstance()
+          .sayHelloFoo();
+
+        assertEquals(r, Bar.sayHelloBar());
+    }
+
+    @Test
+    public void givenMethodName_whenDefineMethod_thenCreateMethod() throws Exception {
+        Class<?> type = new ByteBuddy()
+            .subclass(Object.class)
+            .name("MyClassName")
+            .defineMethod("custom", String.class, Modifier.PUBLIC)
+            .intercept(MethodDelegation.to(Bar.class))
+            .defineField("x", String.class, Modifier.PUBLIC)
+            .make()
+            .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER)
+            .getLoaded();
+
+        Method m = type.getDeclaredMethod("custom", null);
+
+        assertEquals(m.invoke(type.newInstance()), Bar.sayHelloBar());
+        assertNotNull(type.getDeclaredField("x"));
+
+    }
+
+
+}