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fabric-sdk-java How to implement the Network.addBlockListener method in my App.java

I am new to Hyperlegder-Fabric and already manage to connect to a network through the org.hyperledger.fabric.gateway package.
This is my App.java class:
//Fabric Imports
import org.hyperledger.fabric.gateway.*;
import org.hyperledger.fabric.sdk.BlockEvent;
import org.hyperledger.fabric.sdk.ChaincodeEventListener;
//Other Imports
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.InvalidKeyException;
import java.security.PrivateKey;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.util.concurrent.TimeoutException;
import java.util.function.Consumer;
public class App{
public static void main(String[] args) throws IOException {
// Load an existing wallet holding identities used to access the network.
Path walletDirectory = Paths.get("wallet");
Wallet wallet = Wallets.newFileSystemWallet(walletDirectory);
// Path to a common connection profile describing the network.
Path networkConfigFile = Paths.get("connection.json");
// Configure the gateway connection used to access the network.
Gateway.Builder builder = Gateway.createBuilder()
.identity(wallet, "user1")
.networkConfig(networkConfigFile);
// Create a gateway connection
try (Gateway gateway = builder.connect()) {
// Obtain a smart contract deployed on the network.
Network network = gateway.getNetwork("mychannel");
Contract contract = network.getContract("fabcar");
// Submit transactions that store state to the ledger.
byte[] createCarResult = contract.createTransaction("createCar")
.submit("CAR10", "VW", "Polo", "Grey", "Mary");
System.out.println(new String(createCarResult, StandardCharsets.UTF_8));
// Evaluate transactions that query state from the ledger.
byte[] queryAllCarsResult = contract.evaluateTransaction("queryAllCars");
System.out.println(new String(queryAllCarsResult, StandardCharsets.UTF_8));
} catch (ContractException | TimeoutException | InterruptedException e) {
e.printStackTrace();
}
}
}
Now I need to listen for block events, so I see in the documentation that the Network package contains the addBlockListener method (https://hyperledger.github.io/fabric-gateway-java/release-2.2/org/hyperledger/fabric/gateway/Network.html)
My doubt is how i can implement this method in the above App.java file so i can get the block number, etc. I am not a java developer i am struggling a lot on this since.
Appreciate any help.

The listener you attach is an implementation of the Consumer<BlockEvent> type, where Consumer is a standard Java functional interface:
https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/function/Consumer.html
To define your listener you could:
write your own listener class that implements that interface; or
define an anonymous class in-line that implements that interface; or
use a lambda expression as a short-hand for the anonymous class implementation to minimise boiler-plate code.
Using a lambda expression, your code might look like this:
network.addBlockListener(blockEvent -> {
long blockNumber = blockEvent.getBlockNumber();
System.out.println("Received block number " + blockNumber);
});
If you add the listener to the network before submitting your transaction, you should see the block event created when your submitted transaction is recorded on the ledger.

Java Network Simulator Getting Started

I am working on simulating a network topology with Java Network Simulator(JNS). I have followed the tutorial which is in documentation of JNS download. Following is the code of the example:
package simulator_;
import java.awt.peer.TextComponentPeer;
import java.io.IOException;
import jns.Simulator;
import jns.element.DuplexInterface;
import jns.element.DuplexLink;
import jns.element.Interface;
import jns.element.Link;
import jns.element.Node;
import jns.trace.Event;
import jns.trace.Trace;
import jns.util.IPAddr;
public class simu {
public static void main(String[] args) {
Simulator sim=Simulator.getInstance();
Node src=new Node("Source node");
Node router=new Node("Router");
Node dest=new Node("Destination node");
sim.attach(src);
sim.attach(router);
sim.attach(dest);
Interface src_iface=new DuplexInterface(new IPAddr(192,168,1,10));
src.attach(src_iface);
sim.attach(src_iface);
Interface dest_iface=new DuplexInterface(new IPAddr(128,116,11,20));
dest.attach(dest_iface);
sim.attach(dest_iface);
Interface route_iface192=new DuplexInterface(new IPAddr(192,168,1,1));
Interface route_iface128=new DuplexInterface(new IPAddr(128,116,11,1));
router.attach(route_iface192);
router.attach(route_iface128);
sim.attach(route_iface192);
sim.attach(route_iface128);
Link link_src_router=new DuplexLink(1000000,0.001);
Link link_router_dest=new DuplexLink(64000,0.1);
src_iface.attach(link_src_router,true);
route_iface192.attach(link_src_router,true);
sim.attach(link_src_router);
route_iface128.attach(link_router_dest,true);
dest_iface.attach(link_router_dest,true);
sim.attach(link_router_dest);
src.addDefaultRoute(src_iface);
dest.addDefaultRoute(dest_iface);
router.addRoute(new IPAddr(192,168,1,0),new IPAddr(255,255,255,0),
route_iface192);
router.addRoute(new IPAddr(128,116,11,0),new IPAddr(255,255,255,0),
route_iface128);
sim.run();
}
}
The problem I am facing is when I call sim.run(), the program throws me NullPointerException error. I am a newbie in JNS. Kindly guide if how can I successfully create a file foe javis to Simulate with the help of above code. I am using Eclipse IDE.
Thanks in advance.

try setting a trace instance
sim.setTrace(new JavisTrace("output.txt"));

passing argument to WordCram code

I have the following question: I am trying to execute the usConstitution wordcram example (code follows) and if provided as is the code executes in eclipse, the applet starts and the word cloud is created. (code follows)
import processing.core.*;
//import processing.xml.*;
import wordcram.*;
import wordcram.text.*;
import java.applet.*;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.event.MouseEvent;
import java.awt.event.KeyEvent;
import java.awt.event.FocusEvent;
import java.awt.Image;
import java.io.*;
import java.net.*;
import java.text.*;
import java.util.*;
import java.util.zip.*;
import java.util.regex.*;
public class usConstitution extends PApplet {
/*
US Constitution text from http://www.usconstitution.net/const.txt
Liberation Serif font from RedHat: https://www.redhat.com/promo/fonts/
*/
WordCram wordCram;
public void setup() {
size(800, 600);
background(255);
colorMode(HSB);
initWordCram();
}
public void initWordCram() {
wordCram = new WordCram(this)
.fromTextFile("http://www.usconstitution.net/const.txt")
.withFont(createFont("https://www.redhat.com/promo/fonts/", 1))
.sizedByWeight(10, 90)
.withColors(color(0, 250, 200), color(30), color(170, 230, 200));
}
public void draw() {
if (wordCram.hasMore()) {
wordCram.drawNext();
}
}
public void mouseClicked() {
background(255);
initWordCram();
}
static public void main(String args[]) {
PApplet.main(new String[] { "--bgcolor=#ECE9D8", "usConstitution" });
}
}
My problem is the following:
I want to pass through main (which is the only static class) an argument so as to call the usConstitution.class from another class providing whichever valid filename I want in order to produce its word cloud. So how do I do that? I tried calling usConstitution.main providing some args but when I try to simply print the string I just passed to main (just to check if it is passed) I get nothing on the screen. So the question is How can I pass an argument to this code to customize .fromTextFile inside initWordCram ?
Thank you a lot!

from: https://wordcram.wordpress.com/2010/09/09/get-acquainted-with-wordcram/ :
Daniel Bernier says:
June 11, 2013 at 1:13 am
You can’t pass command-line args directly to WordCram, because it has no executable.
But you can make an executable wrapper (base it on the IDE examples that come with WordCram), and it can read command-line args & pass them to WordCram as needed.
FYI, it’ll still pop up an Applet somewhere – AFAIK, you can’t really run Processing “headless.” But that’s usually only a concern if you’re trying to run on a server.

type cannot be resolved [closed]

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center.
Closed 10 years ago.
heres my code:
import javax.swing.*;
import java.awt.*;
public class FirstGui extends JFrame {
private JLabel label;
private JButton button;
public FirstGui() {
setLayout(new FlowLayout());
button = new JButton("Click for sex");
add(button);
label = new JLabel("");
add(label);
event e = new event();
button.addActionListener(e);
}
public class event implements ActionListener {
public void actionPerformed(ActionEvent e) {
label.setText("how you can see wors here");
}
}
public static void main(String [] args) {
FirstGui gui = new FirstGui();
gui.setDefaultCloseOperation(EXIT_ON_CLOSE);
gui.setSize(200, 200);
gui.setTitle("Title");
gui.setVisible(true);
}
}
And it generates a errors:
ActionEvent cannot be resolved to a type FirstGui.java /Test/src line 26 Java Problem
ActionListener cannot be resolved to a type FirstGui.java /Test/src line 24 Java Problem
The method addActionListener(ActionListener) in the type AbstractButton is not applicable for the arguments (FirstGui.event) FirstGui.java /Test/src line 21 Java Problem
what is wrong with it??? im new to java.

Import the following:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

ActionEvent and ActionListener are located into the java.awt.event package.
Importing java.awt.* is not enough.

Both of these classes require you to import them. You can do so by importing everything in java.awt.event:
import java.awt.event.*;
or you may just want to import specifically what you're using:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
Remember that it's considered good practice to import individual classes (the latter option) instead of importing whole packages.
If you ever get stuck like this again, looking at The Docs for any Java Class will tell you exactly what you need to import with a little diagram that looks like this:
java.lang.Object
java.util.EventObject
java.awt.AWTEvent
java.awt.event.ActionEvent

Java syntax error on token ";" expected [closed]

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center.
Closed 10 years ago.
I have a small problem in my java code. Error is
Syntax error on token ";", , expected
Here is my code:
package natchly.chest;
import natchly.chest.blocks.BlockStoneChest;
import net.minecraft.block.Block;
import cpw.mods.fml.common.Mod;
import cpw.mods.fml.common.Mod.Init;
import cpw.mods.fml.common.network.NetworkMod;
import cpw.mods.fml.common.registry.GameRegistry;
import cpw.mods.fml.common.registry.LanguageRegistry;
import cpw.mods.fml.common.event.FMLInitializationEvent;
#Mod(modid="chestsplus", name="Chests+", version="1.4.6_01")
#NetworkMod(clientSideRequired=true, serverSideRequired=false)
public class ModChests {
public int idBlockStoneChest = 250;
public static Block blockStoneChest; // <-------- Error here
blockStoneChest = new BlockStoneChest(idBlockStoneChest).setBlockName("blockNAZWABLOKU").setHardness(1.5F).setResistance(5.0F);
#Init
public void init(FMLInitializationEvent e) {
GameRegistry.registerBlock(blockStoneChest);
LanguageRegistry.addName(blockStoneChest, "Stone Chest");
}
}

Either do this:
public static Block blockStoneChest = new BlockStoneChest(idBlockStoneChest).setBlockName("blockNAZWABLOKU").setHardness(1.5F).setResistance(5.0F);
Or this:
public static Block blockStoneChest; <-------- Error here
static {
blockStoneChest = new BlockStoneChest(idBlockStoneChest).setBlockName("blockNAZWABLOKU").setHardness(1.5F).setResistance(5.0F);
}

Combine these two lines into one declaration and instantiation step. The way you're doing it isn't permitted in Java unless that's inside of a method.
public static BlockStoneChest blockStoneChest = new BlockStoneChest(idBlockStoneChest).setBlockName("blockNAZWABLOKU").setHardness(1.5F).setResistance(5.0F);