This is a ping utility based on https://gist.github.com/zh32/2b8f00ba6f7cdabef74d

PingExample.java

import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

import java.io.IOException;
import java.net.InetSocketAddress;

public class PingExample {
    private static Gson gson = new Gson();

    public static void main(String[] args) {
        try {
            new ServerListPing(new InetSocketAddress("127.0.0.1", 25565)) {
                @Override
                public void onResponse(String json, int time) {
                    JsonParser parser = new JsonParser();
                    JsonElement element = parser.parse(json);
                    JsonObject object = element.getAsJsonObject();
                    JsonObject version = object.getAsJsonObject("version");
                    int protocol = version.get("protocol").getAsInt();
                    switch (protocol) {
                        case 47:
                        case 5:
                        case 4: {
                            StatusResponse17 response = gson.fromJson(element, StatusResponse17.class);
                            break;
                        }

                        default: {
                            StatusResponse19 response = gson.fromJson(element, StatusResponse19.class);
                        }
                    }
                }
            };
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

ServerListPing.java

import java.io.*;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketException;

public abstract class ServerListPing {
    private final InetSocketAddress host;
    private final int timeout;
    
    public ServerListPing(InetSocketAddress host, int timeout) throws IOException {
    	this.host = host;
    	this.timeout = timeout;
        Socket socket = new Socket();
        OutputStream outputStream;
        DataOutputStream dataOutputStream;
        InputStream inputStream;
        InputStreamReader inputStreamReader;

        socket.setSoTimeout(this.timeout);

        socket.connect(host, timeout);

        outputStream = socket.getOutputStream();
        dataOutputStream = new DataOutputStream(outputStream);

        inputStream = socket.getInputStream();
        inputStreamReader = new InputStreamReader(inputStream);

        ByteArrayOutputStream b = new ByteArrayOutputStream();
        DataOutputStream handshake = new DataOutputStream(b);
        handshake.writeByte(0x00); //packet id for handshake
        writeVarInt(handshake, 4); //protocol version
        writeVarInt(handshake, this.host.getHostString().length()); //host length
        handshake.writeBytes(this.host.getHostString()); //host string
        handshake.writeShort(host.getPort()); //port
        writeVarInt(handshake, 1); //state (1 for handshake)

        writeVarInt(dataOutputStream, b.size()); //prepend size
        dataOutputStream.write(b.toByteArray()); //write handshake packet


        dataOutputStream.writeByte(0x01); //size is only 1
        dataOutputStream.writeByte(0x00); //packet id for ping
        DataInputStream dataInputStream = new DataInputStream(inputStream);
        int size = readVarInt(dataInputStream); //size of packet
        int id = readVarInt(dataInputStream); //packet id

        if (id == -1) {
            socket.close();
            throw new IOException("Premature end of stream.");
        }

        if (id != 0x00) { //we want a status response
            socket.close();
            throw new IOException("Invalid packetID");
        }
        int length = readVarInt(dataInputStream); //length of json string

        if (length == -1) {
            socket.close();
            throw new IOException("Premature end of stream.");
        }

        if (length == 0) {
            socket.close();
            throw new IOException("Invalid string length.");
        }

        byte[] in = new byte[length];
        dataInputStream.readFully(in);  //read json string
        String json = new String(in);


        long now = System.currentTimeMillis();
        dataOutputStream.writeByte(0x09); //size of packet
        dataOutputStream.writeByte(0x01); //0x01 for ping
        dataOutputStream.writeLong(now); //time!?

        readVarInt(dataInputStream);
        id = readVarInt(dataInputStream);
        if (id == -1) {
            socket.close();
            throw new IOException("Premature end of stream.");
        }

        if (id != 0x01) {
            socket.close();
            throw new IOException("Invalid packetID");
        }
        long pingtime = dataInputStream.readLong(); //read response

        onResponse(json, (int) (now - pingtime));

        dataOutputStream.close();
        outputStream.close();
        inputStreamReader.close();
        inputStream.close();
        socket.close();
    }

    public ServerListPing(InetSocketAddress host) throws IOException {
        this(host, 7000);
    }

    private int readVarInt(DataInputStream in) throws IOException {
        int i = 0;
        int j = 0;
        while (true) {
            int k = in.readByte();
            i |= (k & 0x7F) << j++ * 7;
            if (j > 5) throw new RuntimeException("VarInt too big");
            if ((k & 0x80) != 128) break;
        }
        return i;
    }

    private void writeVarInt(DataOutputStream out, int paramInt) throws IOException {
        while (true) {
            if ((paramInt & 0xFFFFFF80) == 0) {
                out.writeByte(paramInt);
                return;
            }

            out.writeByte(paramInt & 0x7F | 0x80);
            paramInt >>>= 7;
        }
    }

    public InetSocketAddress getHost() {
        return host;
    }

    public int getTimeout() {
        return timeout;
    }

    public abstract void onResponse(String json, int time);
}

StatusResponse17.java

import java.util.List;

public class StatusResponse17 {
	private String description;
	private PingPlayers players;
	private PingVersion version;
	private String favicon;
	private int time;
	
	public String getDescription() {
		return description;
	}
	
	public PingPlayers getPlayers() {
		return players;
	}
	
	public PingVersion getVersion() {
		return version;
	}
	
	public String getFavicon() {
		return favicon;
	}
	
	public int getTime() {
		return time;
	}
	
	public void setTime(int time) {
		this.time = time;
	}
	
	public class PingPlayers {
		private int max;
		private int online;
		private List<PingPlayer> sample;
		
		public int getMax() {
			return max;
		}
		
		public int getOnline() {
			return online;
		}
		
		public List<PingPlayer> getSample() {
			return sample;
		}
	}
	
	public class PingPlayer {
		private String name;
		private String id;
		
		public String getName() {
			return name;
		}
		
		public String getId() {
			return id;
		}
	}
	
	public class PingVersion {
		private String name;
		private int protocol;
		
		public String getName() {
			return name;
		}
		
		public int getProtocol() {
			return protocol;
		}
	}
}

StatusResponse19.java

import java.util.List;

public class StatusResponse17 {
	private String description;
	private PingPlayers players;
	private PingVersion version;
	private String favicon;
	private int time;
	
	public String getDescription() {
		return description;
	}
	
	public PingPlayers getPlayers() {
		return players;
	}
	
	public PingVersion getVersion() {
		return version;
	}
	
	public String getFavicon() {
		return favicon;
	}
	
	public int getTime() {
		return time;
	}
	
	public void setTime(int time) {
		this.time = time;
	}
	
	public class PingPlayers {
		private int max;
		private int online;
		private List<PingPlayer> sample;
		
		public int getMax() {
			return max;
		}
		
		public int getOnline() {
			return online;
		}
		
		public List<PingPlayer> getSample() {
			return sample;
		}
	}
	
	public class PingPlayer {
		private String name;
		private String id;
		
		public String getName() {
			return name;
		}
		
		public String getId() {
			return id;
		}
	}
	
	public class PingVersion {
		private String name;
		private int protocol;
		
		public String getName() {
			return name;
		}
		
		public int getProtocol() {
			return protocol;
		}
	}
}