Add Java test

tests/apps/java/Procfile

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+web:    java -cp target/classes:target/dependency/* HelloWorld

tests/apps/java/check_deploy

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+#!/usr/bin/env bash
+set -e; output="$(curl -s $1)"; echo $output; test "$output" == "Hello from Java!"

tests/apps/java/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.example</groupId>
+    <version>1.0-SNAPSHOT</version>
+    <artifactId>helloworld</artifactId>
+    <dependencies>
+        <dependency>
+            <groupId>org.eclipse.jetty</groupId>
+            <artifactId>jetty-servlet</artifactId>
+            <version>7.6.0.v20120127</version>
+        </dependency>
+        <dependency>
+            <groupId>javax.servlet</groupId>
+            <artifactId>servlet-api</artifactId>
+            <version>2.5</version>
+        </dependency>
+    </dependencies>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-dependency-plugin</artifactId>
+                <version>2.4</version>
+                <executions>
+                    <execution>
+                        <id>copy-dependencies</id>
+                        <phase>package</phase>
+                        <goals><goal>copy-dependencies</goal></goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

tests/apps/java/src/main/java/HelloWorld.java

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+import java.io.IOException;
+import javax.servlet.ServletException;
+import javax.servlet.http.*;
+import org.eclipse.jetty.server.Server;
+import org.eclipse.jetty.servlet.*;
+
+public class HelloWorld extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
+            throws ServletException, IOException {
+        resp.getWriter().print("Hello from Java!\n");
+    }
+    public static void main(String[] args) throws Exception{
+        Server server = new Server(Integer.valueOf(System.getenv("PORT")));
+        ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
+        context.setContextPath("/");
+        server.setHandler(context);
+        context.addServlet(new ServletHolder(new HelloWorld()),"/*");
+        server.start();
+        server.join();
+    }
+}