Fix writing issues

Author: Seggan

.gitignore

@@ -1,4 +1,5 @@
 .idea
 target
 JavaClassLib.iml
-dependency-reduced-pom.xml
+dependency-reduced-pom.xml
+Testy.class

src/main/java/io/github/seggan/javaclasslib/JavaClass.java

@@ -45,12 +45,13 @@ public void write(@Nonnull OutputStream out) throws IOException {
         out.write(ByteUtils.twoBytesFromInt(ClassAccessFlags.combine(classAccessFlags)));
         out.write(thisClass.getIndexBytes());
         out.write(superClass.getIndexBytes());
-        out.write(new byte[]{0, 0});
+        out.write(new byte[]{0, 0, 0, 0});
         out.write(ByteUtils.twoBytesFromInt(methods.size()));
         for (Method method : methods) {
             out.write(method.getBytes());
         }
         out.write(0);
+        out.write(0);
     }
 
     public List<ConstantPoolEntry> getConstantPool() {

src/main/java/io/github/seggan/javaclasslib/constantpool/ConstantPoolEntry.java

@@ -30,7 +30,7 @@ public final ConstantPoolTag getTag() {
      * @return the index of this constant pool entry
      */
     public final int getIndex() {
-        return constantPool.indexOf(this);
+        return constantPool.indexOf(this) + 1;
     }
 
     /**

src/test/java/io/github/seggan/javaclasslib/tests/Test.java

@@ -0,0 +1,21 @@
+package io.github.seggan.javaclasslib.tests;
+
+import io.github.seggan.javaclasslib.ClassAccessFlags;
+import io.github.seggan.javaclasslib.JavaClass;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+public class Test {
+
+    public static void main(String[] args) {
+
+        JavaClass javaClass = new JavaClass("Testy", "java.lang.Object", 16);
+        javaClass.setClassAccessFlags(ClassAccessFlags.PUBLIC, ClassAccessFlags.FINAL);
+        try (FileOutputStream outputStream = new FileOutputStream("Testy.class")) {
+            javaClass.write(outputStream);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}