code: public boolean[] getKeyUsage() {
          try {
              String extAlias = OIDMap.getName(PKIXExtensions.KeyUsage_Id);
              if (extAlias == null)
                  return null;
  
              KeyUsageExtension certExt = (KeyUsageExtension)this.get(extAlias);
              if (certExt == null)
                  return null;
  
              boolean[] ret = certExt.getBits();
              if (ret.length < NUM_STANDARD_KEY_USAGE) {
                  boolean[] usageBits = new boolean[NUM_STANDARD_KEY_USAGE];
                  System.arraycopy(ret, 0, usageBits, 0, ret.length);
                  ret = usageBits;
              }
              return ret;
          } catch (Exception e) {
              return null;
          }
      }
docs: Get a boolean array representing the bits of the KeyUsage extension,
  (oid = 2.5.29.15).
  @return the bit values of this extension as an array of booleans.