Let's say I have a package called com.Gazzali and inside this package I've 3 another classes.
package com.Gazzali;
//Driver class
public class Main {
public static void main(String[] args) {
System.out.println("Hey There !");
FireCall target = new FireCall(); // calls 2nd class (named: Firecall)
target.callfired();
}
}
2nd class:
package com.Gazzali;
public class FireCall {
public void callfired()
{
System.out.println("Calling function Triggered.");
Execute Fire = new Execute(); //calls 3rd class (named : Execution).
if(Fire.click() == 1)
System.out.println("You're Dead, Boy !!!");
else
System.out.println("Whoooss Saved !!!");
}
}
3rd class:
package com.Gazzali;
import java.util.Scanner;
public class Execute {
int choice;
Scanner query = new Scanner(System.in);
public int click()
{
System.out.println("Enter a choice : ");
choice = query.nextInt();
if(choice % 2 == 0)
{
return 1;
}
else
return 0;
}
}
these 3 comprises my com.Gazzali package. Now in another file (RunPackTest.java) I want to call the main method of Main class (Driver class). So I tried importing like below:
import com.Gazzali.Main;
public class RunPackTest {
public static void main(String[] args) {
Main run = new Main(); //calling Main method of Driver class of the package
System.out.println(run); //Doesn't seem to work,IDE only return 0
}
}
How to do this? beacuse the main method of Main class starts the program and calls another classess of the package accordingly.
I believe this would do it:
import com.Gazzali.Main;
public class RunPackTest {
public static void main(String[] args) {
Main.main(null);
}
}
You can call main just like any other method, although it's not good practice in general.
Related
What's the issue here?
class UserInput {
public void name() {
System.out.println("This is a test.");
}
}
public class MyClass {
UserInput input = new UserInput();
input.name();
}
This complains:
<identifier> expected
input.name();
Put your code in a method.
Try this:
public class MyClass {
public static void main(String[] args) {
UserInput input = new UserInput();
input.name();
}
}
Then "run" the class from your IDE
You can't call methods outside a method. Code like this cannot float around in the class.
You need something like:
public class MyClass {
UserInput input = new UserInput();
public void foo() {
input.name();
}
}
or inside a constructor:
public class MyClass {
UserInput input = new UserInput();
public MyClass() {
input.name();
}
}
input.name() needs to be inside a function; classes contain declarations, not random code.
Try it like this instead, move your myclass items inside a main method:
class UserInput {
public void name() {
System.out.println("This is a test.");
}
}
public class MyClass {
public static void main( String args[] )
{
UserInput input = new UserInput();
input.name();
}
}
I saw this error with code that WAS in a method; However, it was in a try-with-resources block.
The following code is illegal:
try (testResource r = getTestResource();
System.out.println("Hello!");
resource2 = getResource2(r)) { ...
The print statement is what makes this illegal. The 2 lines before and after the print statement are part of the resource initialization section, so they are fine. But no other code can be inside of those parentheses. Read more about "try-with-resources" here: https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html
I'm writing some code for a text based game for my Computer Science class, but I'm having some problems with this code
(java code).
The all the code works until I put in the if/else statements, so I want to know where I should be putting the statements at.
(Error Message)
Code:
import java.util.Scanner;
import java.util.ArrayList;
class Progress {
public String udc;
public String u = "up";
public String d = "down";
public void start() {
System.out.println("Hello.");
}
public void c1() {
Scanner name=new Scanner(System.in);
System.out.println("What's your name?");
System.out.println("Hello "+name.nextLine()+".");
}
public void uod() {
Scanner ud = new Scanner(System.in);
System.out.println("Up or down?");
udc = ud.nextLine();
}
public void uodc() {
System.out.println("going "+udc+".");
}
public void end() {
System.out.println("Press any key to exit");
}
}
public class APGame {
public static void main(String[] args) {
Progress p =new Progress();
p.start();
p.c1();
p.uod();
if (u.equals(udc)) {p.uodc();}
else {p.oud();}
p.end();
}}
u and udc variables are defined inside another class, that is Progress, and should be accessed (as they are public), by p.u and p.udc.
if (p.u.equals(p.udc)) ...
udc and u are instance variables of the class Progress. So the problem with the if-else statement is that you are not referencing udc from any object of the Progress class. To fix it do:
if(p.u.equals(p.udc) {
p.uodc();
}else{
p.uod();
}
This question already has answers here:
Error: Main method not found in class Calculate, please define the main method as: public static void main(String[] args) [duplicate]
(5 answers)
Closed 8 years ago.
Error: Main method not found in class MovieDatabase, please define the main method as: public static void main(String[] args) or a JavaFX application class must extend javafx.application.Application
import java.io.FileInputStream;
import java.util.Scanner;
import java.util.Arrays;
public class MovieDatabase {
private int[] analysis;
//creating the contructor
public MovieDatabase(String file){
analysis = new int[2015];
this.load(file);
}
//uses the load(String file) method from downstairs to do all of the work
public void load(String file){
Scanner theScanner = null;
try{
//inputing the into the scanner
theScanner = new Scanner(new FileInputStream(file));
}
catch(Exception ex){
ex.printStackTrace();
}
// as long as the scanner has another line
while(theScanner.hasNextLine())
{
String Line = theScanner.nextLine();
//make an array called split and allocated different elements based on a seperation of ##
String split[] = Line.split("##");
int year = Integer.valueOf(split[1]);
analysis[year] ++;
}
}
//print out the array in the synchronous format
public void print(){
System.out.printf("%1$-30s %2$10s %3$10s %4$10s ", "Year", "Occurances", "", "");
//go through the array
for (int i =0;i < analysis.length ;i++ ) {
if(analysis[i] >0){
for (int j =i;j < analysis.length ;i++ ){
System.out.printf("%1$-30s %2$10s %3$10s %4$10s ", j, analysis[j], "", "");
}
}
}
}
}
How do I fix this error message?
Ive read other similar questions but just say to make the classes public. Mine are public.
main() method in Java is an standard method which is used by JVM to start execution of any Java program. main method is referred as entry point of Java application which is true in case of core java application
You have missed it. Add following main() method
public static void main(String[] args) {
MovieDatabase db = new MovieDatabase("file/path/goes/here");
db.print();
}
In the Java programming language, every application must contain a
main method whose signature is:
public static void main(String[] args)
As the error suggests, if its non FX project, just define something like:
public static void main(String args[]) {
...
}
Or else change you class definition so it extends Application, something like:
public class MovieDatabase extends Application
To invoke any application JVM need main() method, and which should have following access specifiers and modifiers,
public static void main(String args[])
public - It should be accessible to all
static - JVM not able to create instance of your class so method should be static
void - method not returning anything
For each java application main method is entry point, so your application should have atleast one main method to start execution of application.
It's because you have forgot to add the main method. The error clearly says:
please define the main method as: public static void main(String[]
args)
So add the main:
public static void main(String[] args) {
MovieDatabase m = new MovieDatabase("Your File Path");
m.print();
}
When I play it in NETBEANS IDE 8.0 it keeps saying there is no main class even though I added the main class already?
Need help can't understand.
PS. If I delete the static in magic() it blocks the magic() in main.
package fibotail;
import java.util.Scanner;
public class Fibotail {
public static int fibo(int control, int currentValue, int previousValue) {
if (control < 2) {
return currentValue;
}
return fibo(control - 1, currentValue + previousValue, currentValue);
}
public static void magic() {
String cCharacter;
do {
System.out.println("Input here: ");
int something = new Scanner(System.in).nextInt();
for (int i = 1; fibo(i, 0, 1) <= something; i++) {
System.out.println(fibo(i, 0, 1));
}
do {
System.out.println("Do you want to try again? ");
cCharacter = new Scanner(System.in).next();
} while (!(cCharacter.equals("y") || cCharacter.equals("Y") || cCharacter.equals("N") || cCharacter.equals("n")));
} while (cCharacter.equals('y') || cCharacter.equals('Y'));
}
public static int main(String args[]) {
magic();
return 0;
}
}
Return type should be void, not int:
public static void main(String args[]) { ... }
The JVM looks for the exact signature of the method.
When you run your project you would get:
Error: Main method must return a value of type void in class MainTest, please
define the main method as:
public static void main(String[] args)
In other languages than java, where main returns int (such as C and C++) the return code of main becomes the exit code of the process, which is often used by command interpreters and other external programs to determine whether the process completed successfully.
But java needs void as the return value. (Java internal architecture)
If you reaaly need to return a value just use the following:
System#exit(int)
To enable your program quit with a specific exit code which can be interpreted by the operating system.
Your main() method must have return type void
public static void main(String[] args){
}
Not int or other.
main() method is the entry point of your program and JVM is looking exact main() method.
You have to change your code a little bit. It should be:
public static void main(String args[])
The return type of main method is void
I'm trying to control Bugs in GridWorld. I have tried two ways of doing this, neither of which have actually moved or turned the bug. They both compile but nothing happens.
Here is the Bug that will be controlled:
package info.gridworld.actor;
import info.gridworld.grid.*;
import info.gridworld.grid.Location;
import java.awt.Color;
public class MazeBug extends Bug {
public MazeBug() {
super(Color.blue);
}
public void forward(){
Grid<Actor> gr = getGrid();
if (gr == null)
return;
Location loc = getLocation();
Location next = loc.getAdjacentLocation(getDirection());
if (gr.isValid(next))
moveTo(next);
else
removeSelfFromGrid();
}
public void turnRight(){
setDirection(getDirection() + Location.RIGHT);
}
public void turnLeft(){
setDirection(getDirection() + Location.LEFT);
}
}
Here is the first way that I tried controlling the bugs with the keys W,A, and D using Scanner (not sure if I used scanner correctly)
package info.gridworld.actor;
import java.util.Scanner;
import info.gridworld.grid.*;
public class KeyTests extends Actor
{
public static ActorWorld world = new ActorWorld(new BoundedGrid<Actor>(20, 20));
public static MazeBug currentBug;
public static void main(String[] args) {
world.show();
world.add(new Location(1,11),new MazeBug());
while(true){
Scanner k = new Scanner(System.in);
String buttonpress = k.nextLine();
if (buttonpress.equals("w"))
currentBug.forward();
if (buttonpress.equals("d"))
currentBug.turnRight();
if (buttonpress.equals("a"))
currentBug.turnLeft();
}
}
}
Here is the 2nd way I tried to control the bug
package info.gridworld.actor;
import info.gridworld.grid.*;
public class KeyTests extends Actor
{
public static ActorWorld world = new ActorWorld(new BoundedGrid<Actor>(20, 20));
public static MazeBug currentBug;
public static void main(String[] args) {
world.add(new Location(1,11),new MazeBug());
java.awt.KeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(new java.awt.KeyEventDispatcher() {
public boolean dispatchKeyEvent(java.awt.event.KeyEvent event) {
String key = javax.swing.KeyStroke.getKeyStrokeForEvent(event).toString();
if (key.equals("w"))
currentBug.forward();
if (key.equals("d"))
currentBug.turnRight();
if (key.equals("a"))
currentBug.turnLeft();
world.show();
return true;
}
});
world.show();
}
}
Thanks for any help in advanced
I am almost positive that your problem is that you put your controlling code in the Runner instead of your Bug's act method.
When GridWorld steps all it does is call each Actor's act method, so if your Actor has an unpopulated method it will just call the parent, or do nothing. Your runner, since it is not an 'Actor' has no act method, and after the first run is never looked at again.
Try this in your MazeBug:
public void act()
{
java.awt.KeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(new java.awt.KeyEventDispatcher() {
public boolean dispatchKeyEvent(java.awt.event.KeyEvent event) {
String key = javax.swing.KeyStroke.getKeyStrokeForEvent(event).toString();
if (key.equals("w"))
forward();
if (key.equals("d"))
turnRight();
if (key.equals("a"))
turnLeft();
return true;
}
});
}
Note: I have never used EventListeners so can't help with that code.