code: public void setWarnings(String warnings) {
          try {
              deprecationWarnings = CompilerOptions.DeprecationWarnings
                      .fromString(warnings);
          } catch (IllegalArgumentException e) {
              throw new BuildException("invalid value for warnings: " + warnings);
          }
      }
docs: Determines whether deprecation warnings are emitted and if so, whether to
  treat them as fatal errors.
  
  @param warnings string value of CompilerOptions.DeprecationWarnings