BAEL-2452: Using curl from Java (#6043)

* BAEL-2452: Using curl from Java

* A re-do of the examples using tests, instead of main class

* Fix un-used variable

core-java/src/test/java/com/baeldung/curltojava/JavaCurlExamplesUnitTest.java

@@ -0,0 +1,55 @@
+package com.baeldung.curltojava;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.HttpURLConnection;
+import java.net.URL;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class JavaCurlExamplesUnitTest {
+
+
+    @Test
+    public void givenCommand_whenCalled_thenProduceZeroExitCode() throws IOException {
+        String command = "curl --location --request GET \"https://postman-echo.com/get?foo1=bar1&foo2=bar2\"";
+        ProcessBuilder processBuilder = new ProcessBuilder(command.replaceAll("\"", "").split(" "));
+        processBuilder.directory(new File("/home/"));
+        Process process = processBuilder.start();
+        InputStream inputStream = process.getInputStream();
+        // Consume the inputStream so the process can exit
+        JavaCurlExamples.consumeInputStream(inputStream);
+        int exitCode = process.exitValue();
+        
+        Assert.assertEquals(0, exitCode);
+    }
+    
+    @Test
+    public void givenNewCommands_whenCalled_thenCheckIfIsAlive() throws IOException {
+        String command = "curl --location --request GET \"https://postman-echo.com/get?foo1=bar1&foo2=bar2\"";
+        ProcessBuilder processBuilder = new ProcessBuilder(command.replaceAll("\"", "").split(" "));
+        processBuilder.directory(new File("/home/"));
+        Process process = processBuilder.start();
+        
+        // Re-use processBuilder
+        processBuilder.command(new String[]{"newCommand", "arguments"});
+        
+        Assert.assertEquals(true, process.isAlive());
+    }
+
+    @Test
+    public void whenRequestGet_thenReturnSuccessResponseCode() throws IOException {
+        String url = "https://postman-echo.com/get?foo1=bar1&foo2=bar2";
+        URL urlObj = new URL(url);
+        HttpURLConnection connection = (HttpURLConnection) urlObj.openConnection();
+        connection.setDoOutput(true);
+        connection.setInstanceFollowRedirects(false);
+        connection.setRequestMethod("GET");
+        connection.connect();
+        
+        Assert.assertEquals(HttpURLConnection.HTTP_OK, connection.getResponseCode());
+    }
+
+}