// send a read request to the KNX actuator
client.readRequest(knxGroupAddress);         

// this is the status pool that holds all status information which have been requested
var statusPool = client.getStatusPool();     
// the status pool will translate the byte array from KNX into boolean value
var isLampOn = statusPool.getValue(knxGroupAddress, DPT1.SWITCH).getValue();  

var writeGroupAddress = GroupAddress.of(1, 2, 0);
var dpt = "1.001";  // KNX data point type ID (=DPT1.SWITCH)
var values = new String[]{"on", "off", "on", "off"};

// iterate for each value
for (final String value : values) {
    // translate the human-friendy text into a KNX compatible data point value of DPT 1.001
    // and send to the KNX actuator
    var knxValue = DataPointRegistry.getDataPointType(dpt).of(value);
    client.writeRequest(writeGroupAddress, knxValue);
}

var readGroupAddress = GroupAddress.of(1, 2, 3);    // the KNX Group address to fetch the current lamp status
var writeGroupAddress = GroupAddress.of(1, 2, 0);   // the KNX Group Address for set new lamp value ('on' or 'off')

// send read request and fetch the current lamp status 
client.readRequest(readGroupAddress);
var lampStatus = client.getStatusPool().getValue(readGroupAddress, DPT1.SWITCH).getValue();

// toggle the value (off -> on, on -> off)
var lampStatusInverted = !lampStatus;

// now send the write request to set the new lamp status
client.writeRequest(writeGroupAddress, DPT1.SWITCH.of(lampStatusInverted));