Yes there is a workaround, with list of SubnetUtils objects, as you mentioned:
CIDR Signature: [0.255.255.255/1] Netmask: [128.0.0.0]
First Address: [0.0.0.0]
Last Address: [127.255.255.255]
CIDR Signature: [255.255.255.255/1] Netmask: [128.0.0.0]
First Address: [128.0.0.0]
Last Address: [255.255.255.255]
Or with Java code:
SubnetUtils subnetUtils1 = new SubnetUtils("0.255.255.255/1");
SubnetUtils subnetUtils2 = new SubnetUtils("255.255.255.255/1");