title: How to change methods in .class file without recompiling
body: <p>I need to change existing compiled <strong>.class</strong> file. Actually I have even sources of it, but I cannot just change and recompile it because of many dependencies that I don't have. </p>
  
  <p>So I need to change 2 methods. Both them have <strong>void</strong> return type. The first contains just 2 lines that are calls of another methods of the same class, i.e. </p>
  
  <pre><code>public void a() {
      System.out.println("a");
  }
  
  public void b() {
      System.out.println("b");
  }
  
  public void ca() {
      a();
      b();
  
  }
  </code></pre>
  
  <p>And I need to change method <strong>ca</strong> sp that it calls only a() method. </p>
  
  <p>The second method that I need to change contains some logic, but I want to clear it at all, i.e. to have method with empty body that does nothing. </p>
  
  <p>How can I do this? </p>