public static void checkProxyPortProperty() throws NumberFormatException {
    checkNumericSystemProperty("http.proxyPort", Range.closed(0, 65535));
    checkNumericSystemProperty("https.proxyPort", Range.closed(0, 65535));
  }
@Test
  public void testCheckHttpProxyPortProperty_negativeValue() {
    System.setProperty("http.proxyPort", "-1");
    System.clearProperty("https.proxyPort");
    try {
      JibSystemProperties.checkProxyPortProperty();
      Assert.fail();
    } catch (NumberFormatException ex) {
      Assert.assertEquals("http.proxyPort cannot be less than 0: -1", ex.getMessage());
    }

    System.clearProperty("http.proxyPort");
    System.setProperty("https.proxyPort", "-1");
    try {
      JibSystemProperties.checkProxyPortProperty();
      Assert.fail();
    } catch (NumberFormatException ex) {
      Assert.assertEquals("https.proxyPort cannot be less than 0: -1", ex.getMessage());
    }
  }