I've got a problem: I can go fine between classes in my Elipse java project, if they are like this
public class Comienzo {
public static void main() {}
}
But not if they're like this
public class Principal {
public static void main(String args[]) {}
}
I'm yet noobish programmer, so I'm not sure if this is about String args[], but if I delete them Eclipse tell me something's wrong and string args are needed.
So I'm with my class Principal, click a button and
Comienzo.main();
moves from Principal to Comienzo, but if I press a cancel button on Comienzo, I'd like to go back to Principal, but that's the problem, I can't do
Principal.main(String args[]);
because in Comienzo class string cannot be resolved into a variable, and well, I'm not sure what path should I take to go back to Principal class.
Thanks for the comments, the answer is inside the comments.
If you really want to call main( String args[] ) you can do it as follows main(new String[]{});
Related
I am using JsfCaptcha in an attempt to process offline captcha validation. While there is a method to validate "what the user entered matches what the captcha image has shown", I am having a hard time actually printing out what the server states is the right solution. I anticipated this being fairly easy to complete, but for the life of me, cannot figure it out. Here is how I am using the library:
import botdetect.web.jsf.JsfCaptcha;
[...]
#ManagedBean
#RequestScoped
public class MySampleBean implements Serializable {
private JsfCaptcha captcha;
private String captchaCode;
getters for above two fields
[...]
setters for above two fields
[...]
public boolean checkInputMatches() {
if (!this.captcha.validate(captchaCode)) {
return true;
}
return false;
}
}
The method checkInputMatches() demonstrates how the library validates that the user has entered in the right captcha solution. What I'd want to do now is, for debugging purposes, is to log out what the solution was ( In the event that the user entered in the wrong value ). Potentially, something like this:
final String solution = captcha.getCorrectSolutionToCaptcha();
At first, I've taken a look through all of the public getters, but none of them are blatant in providing me the data I need. After trying all of them, I went down the jdgui route, where I decompiled the libraries and tried to hunt my way around to a solution / method that would give me this data.
Sadly, the JsfCaptcha class goes under 5-6 levels of base class extending, with a multitude of protected / private methods. Obviously, a very tedious and unnecessary hunt for something very simple.
Is it possible to print out the actual JsfCaptcha value that is being validated against?
I finally managed to solve the problem with javassist, by modifying the generated bytecode of the Botdetect library. I did this because I was unable to find any getter method for accessing the actual captcha solution. Obviously, this is not a clean solution, but it is a solution given that you just want to debug your code to determine why the code you entered does not match the code that the backend server has. For now, I'll consider this as a solution until there is a cleaner alternative requiring no bytecode manipulation. Here are the details on the version that I played with and got this to work:
botdetect-4.0.beta3.5jar
botdetect-jsf20-4.0.beta3.5.jar
botdetect-servlet-4.0.beta3.5.jar
When the checkInputMatches() method executes to validate the captcha, this structure is executed on the backend with respect to the mentioned jars:
Step 1: ( botdetect-jsf20-4.0.beta3.5.jar )
com.captcha.botdetect.web.jsf.JsfCaptcha ->
public boolean validate(String paramString)
Step 2: ( botdetect-servlet-4.0.beta3.5.jar )
com.captcha.botdetect.web.servlet.Captcha ->
public boolean validate(String paramString)
Step 3: ( botdetect-jsf20-4.0.beta3.5.jar )
com.captcha.botdetect.internal.core.CaptchaBase ->
public boolean validate(String paramString1, String paramString2, ValidationAttemptOrigin paramValidationAttemptOrigin, boolean paramBoolean)
Step 4: ( botdetect-jsf20-4.0.beta3.5.jar )
com.captcha.botdetect.internal.core.captchacode.CodeCollection ->
public final boolean a(String paramString1, String paramString2, Integer paramInteger, boolean paramBoolean, ValidationAttemptOrigin paramValidationAttemptOrigin)
Step 5: Observe $3 ( third argument from Step 4 ) to show the actual code.
Here is a photo using jdgui, through which I came to this conclusion:
With that in mind, here is how you can go about printing that value out when that code is executed using javassits ( I am using javassist-3.18.1-GA.jar , on Tomcat ) :
#ManagedBean(eager = true)
#ApplicationScoped
public class CustomBean implements Serializable {
private static final long serialVersionUID = 3121378662264771535L;
private static Logger LOG = LogManager.getLogger(CustomBean.class.getName());
#PostConstruct
public void initialize() {
try {
final ClassPool classPool = new ClassPool(ClassPool.getDefault());
classPool.insertClassPath(new ClassClassPath(this.getClass()));
classPool.insertClassPath(new LoaderClassPath(Thread.currentThread().getContextClassLoader()));
final CtClass codeCollectionClass = classPool
.get("com.captcha.botdetect.internal.core.captchacode.CodeCollection");
if (!codeCollectionClass.isFrozen()) {
final CtMethod aMethod = codeCollectionClass.getDeclaredMethod("a",
new CtClass[] { classPool.get("java.lang.String"), classPool.get("java.lang.String"),
classPool.get("java.lang.Integer"), classPool.get("boolean"),
classPool.get("com.captcha.botdetect.internal.core."
+ "captchacode.validation.ValidationAttemptOrigin") });
aMethod.insertAfter("System.out.println(\"Botdetect-DEBUG: entered-captcha: \" + "
+ "$1 + \"; expected-captcha: \" + $3 + \";\" );");
codeCollectionClass.toClass();
} else {
LOG.error("Frozen class : Unable to re-compile BotDetect for debugging.");
}
} catch (final Exception e) {
LOG.error("unable to modify the bot detect java code", e);
}
}
}
Given this input and challenge:
You get a message like this in your logs:
Botdetect-DEBUG: entered-captcha: U33aZ; expected-captcha: U49a6;
I can't seem to make this work let alone compile and I am at loss at how to fix it. My teacher gave us the following code (simplified for question's sake):
public static void doing1(String s) {
// add code here
}
public static void doing2(char start, char end) {
// add code here
}
public static int doing3(int num) {
// add code here
}
public static void doing4(Scanner keyboard) {
// add code here
}
I know what needs to go in each method (the work I mean) I just don't know how to print it out in the main method. We cannot change the code given to us, only add to it.
Thank you!
Overloading a method means having the same method name but the method signature (the parameters passed in) is different. So, what you have isn't actually an overload, it is for unique methods because they all have different names. As far as not compiling... what you posted looks fine - perhaps you have an error above or below that code. I believe this is what you are looking for:
public static void doing(String s) {
// add code here
}
public static void doing(char start, char end) {
// add code here
}
public static int doing(int num) {
// add code here
}
public static void doing(Scanner keyboard) {
// add code here
}
Here's a reference on overloads from the almighty John Skeet
I am using Xamarin.iOS. I have created UIView with a few UITextFields. I am looking for best way to initialize text value in these textfields from code.
I can pass text data in the constructor of UIViewContoller, but I don't have access to textFields inside it (they are null). I can change text value of textFields in viewDidLoad method.
I don't want to create additional fields in controller class to store data passed by constructor and use them in viewDidLoad. Do you know better solution ?
I don't want to create additional fields in controller class to store
data passed by constructor and use them in viewDidLoad.
But that's how it's meant to be done.
Alternatively, you can create less fields/properties in your viewcontroller if you use a MVVM pattern:
public class UserViewModel {
public string Name { get; set;}
public string Title { get; set;}
}
public class UserViewController : UIViewController
{
UserViewModel viewModel;
public UserViewController (UserViewModel viewModel) : base (...)
{
this.viewModel = viewModel;
}
public override void ViewDidLoad ()
{
userName.Text = viewModel.Name;
userTitle.Text = viewModel.Title;
}
}
That's the kind of pattern which gives you a lot of code reuse accross platforms (android, WP, ...) and clearly separate concerns. It's a (very) little bit of extra code, but it's worth every byte.
I've got an IClaimsPrincipal variable, and I'd like to see how many claims are in it. Navigating through the properties in the watch window is complicated, so I'd like to customize how this object is displayed.
I'm aware of the [DebuggerTypeProxy] attribute, which initially looked like it might do what I want. Unfortunately, it needs to be attached to the class, and I don't "own" the class. In this case it's a Microsoft.IdentityModel.Claims.ClaimsPrincipal.
I'd like to display the value of IClaimsPrincipal.Identities[0].Claims.Count.
Is there any way, using [DebuggerTypeProxy] or similar, to customize how the value of a type that I don't own is displayed in the watch window?
Example of DebuggerTypeProxyAttribute applied to KeyValuePair showing only the Value member:
using System.Collections.Generic;
using System.Diagnostics;
[assembly: DebuggerTypeProxy(typeof(ConsoleApp2.KeyValuePairDebuggerTypeProxy<,>), Target = typeof(KeyValuePair<,>))]
// alternative format [assembly: DebuggerTypeProxy(typeof(ConsoleApp2.KeyValuePairDebuggerTypeProxy<,>), TargetTypeName = "System.Collections.Generic.KeyValuePair`2")]
namespace ConsoleApp2
{
class KeyValuePairDebuggerTypeProxy<TKey, TValue>
{
private KeyValuePair<TKey, TValue> _keyValuePair; // beeing non-public this member is hidden
//public TKey Key => _keyValuePair.Key;
public TValue Value => _keyValuePair.Value;
public KeyValuePairDebuggerTypeProxy(KeyValuePair<TKey, TValue> keyValuePair)
{
_keyValuePair = keyValuePair;
}
}
class Program
{
static void Main(string[] args)
{
var dictionary = new Dictionary<int, string>() { [1] = "one", [2] = "two" };
Debugger.Break();
}
}
}
Tested on Visual Studio 2017
The best I've come up with so far is to call a method:
public static class DebuggerDisplays
{
public static int ClaimsPrincipal(IClaimsPrincipal claimsPrincipal)
{
return claimsPrincipal.Identities[0].Claims.Count;
}
}
...from the watch window:
DebuggerDisplays.ClaimsPrincipal(_thePrincipal),ac = 10
The ",ac" suppresses the "This expression causes side effects and will not be evaluated".
However, note that when this goes out of scope, Visual Studio will simply grey out the watch window entry, even with the ",ac". To avoid this, you'll need to ensure that everything is fully qualified, which means that you'll end up with extremely long expressions in the watch window.
Hi I'm completely new to android programming and use AIDE via tablet.
I'm trying to create a very basic program with a Spinner box that gives output on the selection Ive made via an TextView or System.Out.printIn. (Perhaps the next step up from Hello world - if you will)
For some reason that I cannot fathom,the compiler refuses to recognise the OnClickListener and gives the error message 'Unknown method OnClickListener in Android.Widget.Spinner'
When I have already checked this in the imports.
As a matter of interest I have changed the name of the Spinner and the error seems to dissapear, the problem then is the Spinner name. I have tried several variations on this, and have came to the conclusion that the best option for me is to create a variable just after Main Acivity, and before the layout is declared.
I have also disabled one of the overrides in order to resolve my problem
has anyone got an idea what the problem could be?
package com.BGilbert.AUC;
import android.app.*;
import android.os.*;
import android.widget.*;
import android.view.View.OnClickListener;
import android.widget.Spinner.*;
import android.view.*;
public class MainActivity extends Activity {;
String Fbstring;
OnClickListener Myonclick;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.main);
final Spinner Fbspinner=(Spinner)findViewById(R.id.Spinner);
// The problem is with this line. OnClickListener just wont be
// recognised
Fbspinner.OnClickListener(Myonclick);
}
// Override previously disabled
#Override
public void Onselect(AdapterView<?> parent,View V, int pos, long id) {
Fbstring = parent.getItemAtPosition(pos).toString();
System.out.println(Fbstring);
}
#Override
public void onNothingSelected(AdapterView<?> arg0) {
}
}
You can't set an onClickListener on a spinner, only on it's views which is too advanced for you at the moment. Instead, use an onItemSelectedListener.
public class MainActivity extends Activity extends Activity implements OnItemSelectedListener {
public void onItemSelected(AdapterView<?> parent, View view,
int pos, long id) {
...
...
}
You should read the documentation first http://developer.android.com/guide/topics/ui/controls/spinner.html
Also try to use standard naming conventions:
http://www.oracle.com/technetwork/java/codeconv-138413.html
http://www.oracle.com/technetwork/java/javase/documentation/codeconventions-135099.html#367
Finally, you have many problems in this code, e.g.
public class MainActivity extends Activity {;
Note the semicolon at the end.
Get your code compiling first, then come back with your next question.
Good luck