title: How can I rewrite this method to remove redundant if statement?
body: <p>How can I rewrite this method to maximum code efficiency and minimize the code length?</p>
  
  <p><strong>Note</strong>: <code>HEADER</code> is a constant defined before.</p>
  
  <pre><code>private static URL getURL(String OS, String type, String size) {
          String prefix = "";
          String prefixLarge = "";
          if (type.equals("image")) {
              prefix = HEADER + "/image";
              prefixLarge = HEADER + "/image_large";
          } else {
              prefix = HEADER + "/file";
              prefixLarge = HEADER + "/file_raw";
          }
          String suffix = ".zip";
          String url = "";
          if (OS.contains("Win7.32bit")) {
              // win7-32bit system
              url = prefix + "Win7.32bit" + suffix;
              if (size.contains("origin")) {
                  url = prefixLarge + "Win7.32bit" + suffix;
              }
          } else if (OS.contains("Win7.64bit")) {
              // win7-64bit system
              url = prefix + "Win7.64bit" + suffix;
              if (size.contains("origin")) {
                  url = prefixLarge + "Win7.64bit" + suffix;
              }
          } else if (OS.contains("WinXP")) {
              // winxp-32bit system
              url = prefix + "WinXP" + suffix;
              if (size.contains("origin")) {
                  url = prefixLarge + "WinXP" + suffix;
              }
          } else if (OS.contains("WinXP.64bit")) {
              // winxp-64bit system
              url = prefix + "WinXP.64bit" + suffix;
              if (size.contains("origin")) {
                  url = prefixLarge + "WinXP.64bit" + suffix;
              }
          } else if (OS.contains("10.04")) {
              // ubuntu10.04 system
              url = prefix + "ubuntu10.04" + suffix;
              if (size.contains("origin")) {
                  url = prefixLarge + "ubuntu10.04" + suffix;
              }
          } else if (OS.contains("12.04")) {
              // ubuntu12.04 system
              url = prefix + "ubuntu12.04" + suffix;
              if (size.contains("origin")) {
                  url = prefixLarge + "ubuntu12.04" + suffix;
              }
          }
          return url;
      }
  </code></pre>