BAEL-5632 add jar example

core-java-modules/core-java-jar/src/main/java/com/baeldung/createjar/Driver.java

@@ -0,0 +1,19 @@
+package com.baeldung.createjar;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.jar.*;
+import com.baeldung.createjar.JarTool;
+
+public class Driver {
+
+    public static void main(String[] args) throws IOException {
+        JarTool tool = new JarTool();
+        tool.startManifest();
+        tool.addToManifest("Main-Class", "com.baeldung.createjar.HelloWorld");
+        JarOutputStream target = tool.openJar("HelloWorld.jar");
+
+        tool.addFile(target, System.getProperty("user.dir") + "\\src\\main\\java", System.getProperty("user.dir") + "\\src\\main\\java\\com\\baeldung\\createjar\\HelloWorld.class");
+        target.close();
+    }
+}

core-java-modules/core-java-jar/src/main/java/com/baeldung/createjar/HelloWorld.java

@@ -0,0 +1,7 @@
+package com.baeldung.createjar;
+
+public class HelloWorld {
+    public static void main(String[] args) {
+        System.out.println("Hello World!");
+    }
+}

core-java-modules/core-java-jar/src/main/java/com/baeldung/createjar/JarTool.java

@@ -0,0 +1,69 @@
+package com.baeldung.createjar;
+
+import java.io.*;
+import java.util.jar.*;
+
+public class JarTool {
+    private Manifest manifest = new Manifest();
+
+    public void addToManifest(String key, String value) {
+        manifest.getMainAttributes()
+            .put(new Attributes.Name(key), value);
+    }
+
+    public void addDirectoryEntry(JarOutputStream target, String parentPath, File dir) throws IOException {
+        String remaining = "";
+        if (parentPath.endsWith(File.separator))
+            remaining = dir.getAbsolutePath()
+                .substring(parentPath.length());
+        else
+            remaining = dir.getAbsolutePath()
+                .substring(parentPath.length() + 1);
+        String name = remaining.replace("\\", "/");
+        if (!name.endsWith("/"))
+            name += "/";
+        JarEntry entry = new JarEntry(name);
+        entry.setTime(dir.lastModified());
+        target.putNextEntry(entry);
+        target.closeEntry();
+    }
+
+    public void addFile(JarOutputStream target, String rootPath, String source) throws IOException {
+        BufferedInputStream in = null;
+        String remaining = "";
+        if (rootPath.endsWith(File.separator))
+            remaining = source.substring(rootPath.length());
+        else
+            remaining = source.substring(rootPath.length() + 1);
+        String name = remaining.replace("\\", "/");
+        JarEntry entry = new JarEntry(name);
+        entry.setTime(new File(source).lastModified());
+        target.putNextEntry(entry);
+        in = new BufferedInputStream(new FileInputStream(source));
+        byte[] buffer = new byte[1024];
+        while (true) {
+            int count = in.read(buffer);
+            if (count == -1)
+                break;
+            target.write(buffer, 0, count);
+        }
+        target.closeEntry();
+        in.close();
+    }
+
+    public JarOutputStream openJar(String jarFile) throws IOException {
+        JarOutputStream target = new JarOutputStream(new FileOutputStream(jarFile), manifest);
+        return target;
+    }
+
+    public void setMainClass(String mainFQCN) {
+        if (mainFQCN != null && !mainFQCN.equals(""))
+            manifest.getMainAttributes()
+                .put(Attributes.Name.MAIN_CLASS, mainFQCN);
+    }
+
+    public void startManifest() {
+        manifest.getMainAttributes()
+            .put(Attributes.Name.MANIFEST_VERSION, "1.0");
+    }
+}