code: public void setTarget(String target) throws IllegalArgumentException {
          int major, minor;
  
          if (target == null || "1.0".equals(target) || "1.1".equals(target)) {
              major = 45; minor = 3;
              if (target == null) {
                  target = "1.0";
              }
          } else if ("1.2".equals(target)) {
              major = 46; minor = 0;
          } else if ("1.3".equals(target)) {
              major = 47; minor = 0;
          } else if ("1.4".equals(target)) {
              major = 48; minor = 0;
          } else if ("1.5".equals(target)) {
              major = 49; minor = 0;
          } else if ("1.6".equals(target)) {
              major = 50; minor = 0;
          } else if ("1.7".equals(target)) {
              major = 51; minor = 0;
          } else {
              throw new IllegalArgumentException
                  ("Unsupported target version: " + target);
          }
          
          mVersion = (minor << 16) | (major & 0xffff);
          mTarget = target.intern();
      }
docs: Specify what target virtual machine version classfile should generate
  for. Calling this method changes the major and minor version of the
  classfile format.
  
  @param target VM version, 1.0, 1.1, etc.
  @throws IllegalArgumentException if target is not supported