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How do I use value from one class for another class Calling from main method

One.java
public class One {
String asd;
public class() {
asd="2d6"
}
public static void main(String args[]) {
Two a = new Two();
}
}
Two.java
public class Two {
ArrayList<String>data;
String asd;
public Two(String asd){
this.asd=asd;
data.add(this.asd);
}
}
How do I use this asd value of second for third class calling from first class's main method.
**Third class**

Per comments of #Maroun Maroun and #Bennyz, you can create a getter and setter method in your Two class:
import java.util.ArrayList;
public class Two {
ArrayList<String> data;
String asd;
public Two(String asd) {
this.asd = asd;
data = new ArrayList<>(); //<-- You needed to initialize the arraylist.
data.add(this.asd);
}
// Get value of 'asd',
public String getAsd() {
return asd;
}
// Set value of 'asd' to the argument given.
public void setAsd(String asd) {
this.asd = asd;
}
}
A great site to learn about this while coding (so not only reading), is CodeAcademy.
To use it in a third class, you can do this:
public class Third {
public static void main(String[] args) {
Two two = new Two("test");
String asd = two.getAsd(); //This hold now "test".
System.out.println("Value of asd: " + asd);
two.setAsd("something else"); //Set asd to "something else".
System.out.println(two.getAsd()); //Hey, it changed!
}
}
There are also some things not right about your code:
public class One {
String asd;
/**
* The name 'class' cannot be used for a method name, it is a reserved
* keyword.
* Also, this method is missing a return value.
* Last, you forgot a ";" after asd="2d6". */
public class() {
asd="2d6"
}
/** This is better. Best would be to create a setter method for this, or
* initialize 'asd' in your constructor. */
public void initializeAsd(){
asd = "2d6";
}
public static void main(String args[]) {
/**
* You haven't made a constructor without arguments.
* Either you make this in you Two class or use arguments in your call.
*/
Two a = new Two();
}
}
Per comment of #cricket_007, a better solution for the public class() method would be:
public class One {
String asd;
public One(){
asd = "2d6";
}
}
This way, when an One object is made (One one = new One), it has a asd field with "2d6" already.

Java: Inmutable static variable, possible?

I have a class with this, it's an example code, not the real code
private static String className;
public static Wish getInstance(Class<?> clazz) {
if(wish == null)
wish = new Wish();
className = clazz.getName();
return wish;
}
Many classes use this Wish class, then each class should "say" a wish with the className passed in the getInstance method.
Then I have something like this
public class Boy {
private Wish w = Wish.getInstance(Boy.class);
//at this moment the static variable take "com.package.Boy" value
....
}
Another classs
public class Girl {
private Wish w = Wish.getInstance(Girl.class);
//at this moment the static variable take "com.package.Girl" value
....
}
When everybody start to say their wishes, example
public class WishesDay {
private Girl g;
private Boy b;
public void makeYourWish() {
g = new Girl(); //get the com.package.Girl value
b = new Boy(); //get the com.package.Boy value
//sample output "com.package.Boy wants A pink house!"
g.iWish("A pink house!"); // the boys don't want this things :(
b.iWish("A spatial boat!");
}
}
I know that each object have the same copy o the Wish class and the static variable className change when each object (Girl, Boy) call the Wish.getInstance(Class<?> clazz) method.
How can I use a static variable (I want avoid to instantiate the Wish class) and keep the correct value for the variable className.
Can I make this with a static variable? or the solution is to instantiate (no static variable)
For example, log4j has the Logger class, I want to make the same thing with the class name.

You'll have to make your constructor private if you want to avoid instantiate the Wish class and make the className not static.
public class Wish {
String className;
private Wish(String className){
this.className = className;
}
public static Wish getInstance(Class<?> clazz) {
String className = clazz.getName();
return new Wish(className);
}
public String getClassName() {
return className;
}
}
package com.test;
public class WishesDay {
private Girl g;
private Boy b;
public void makeYourWish() {
g = new Girl(); //get the com.package.Girl value
b = new Boy(); //get the com.package.Boy value
//sample output "com.package.Boy wants A pink house!"
g.iWish("A pink house!"); // the boys don't want this things :(
b.iWish("A spatial boat!");
}
public static void main(String[] args) {
WishesDay wd = new WishesDay();
wd.makeYourWish();
//outputs com.test.Girl wants A pink house!
//com.test.Boy wants A spatial boat!
}
}

How can a static method change a variable? (Java)

I have this class:
class Inventory {
boolean smallknife = false;
boolean SRLockerkey = false;
void checkinv () {
System.out.println("You have the following items in your inventory: ");
System.out.println(smallknife);
System.out.println(SRLockerkey);
}
}
The Inventory test class
class InvTester {
public static void main(String args[]) {
Inventory TestInv = new Inventory();
System.out.println("This program tests the Inventory");
SKTrue.truth(TestInv.smallknife);
TestInv.checkinv();
}
}
and this class with a method to try to change the inventory
class SKTrue {
static boolean truth(boolean smallknife) {
return true;
}
}
class SKTrue {
static void truth(boolean smallknife) {
smallknife = true;
}
}
I would like to avoid using TestInv.smallknife = SKTrue.truth(TestInv.smallknife) and still change the variable but with a method. Is there a way that this can be done? I want that the truth method does the variable changing and I don't want to do the pass by reference part in the Inventory Test class. Thanks. Is there a way to do this in Java? (I also tried the second version which I think makes more sense)

Assuming you don't want to reference the variables directly (i.e. TestInv.smallknife = blah), the best practice in Java is to declare the variables as private and access them by getters/setters, e.g.:
class Inventory {
private boolean smallknife;
public boolean isSmallknife() {
return smallknife;
}
public void setSmallknife(boolean smallknife) {
this.smallknife = smallknife;
}
}
Now, you can do this:
Inventory TestInv = new Inventory();
TestInv.setSmallknife(SKTrue.truth(blah));
It is called Encapsulation, you can read more about it here.

Passing String from one class to another

How can I pass string variable or String object from one class to another?
I've 2 days on this problem.
One class get data from keyboard and second one should print it in console.

Take some help from the below code:-
public class ReadFrom {
private String stringToShow; // String in this class, which other class will read
public void setStringToShow(String stringToShow) {
this.stringToShow = stringToShow;
}
public String getStringToShow() {
return this.stringToShow;
}
}
class ReadIn {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in); // for taking Keyboard input
ReadFrom rf = new ReadFrom();
rf.setStringToShow(sc.nextLine()); // Setting in ReadFrom string
System.out.println(rf.getStringToShow()); // Reading in this class
}
}

There are two ways:
create an instance of your printer class and evoke the method on the printer object:
public class MyPrinter
{
public void printString( String string )
{
System.out.println( string );
}
}
in your main:
MyPrinter myPrinter = new MyPrinter();
myPrinter.printString( input );
or 2. you create a static method in your printer class and evoke it in your main:
public class MyPrinter
{
public static void printStringWithStaticMethod(String string)
{
System.out.println(string);
}
}
in your main:
MyPrinter.printStringWithStaticMethod( input );

Write a method inside your second class with System.out.println(parameter);
Make the method static and then invoke this in first method like
ClassName.methodName(parameter)

Inside class that accepts Scanner input
variableName ClassName = new Classname();
variablename.methodToPrintString(string);
A textbook can always help in this situation.

Java-How do I call a class with a string?

I am a beginner programmer and this is my first question on this forum.
I am writing a simple text adventure game using BlueJ as a compiler, and I am on a Mac. The problem I ran into is that I would like to make my code more self automated, but I cannot call a class with a string. The reason I want call the class and not have it all in an if function is so that I may incorporate more methods.
Here is how it will run currently:
public class textadventure {
public method(String room){
if(room==street){street.enterRoom();}
}
}
public class street{
public enterRoom(){
//do stuff and call other methods
}
}
The if statement tests for every class/room I create. What I would like the code to do is automatically make the string room into a class name that can be called. So it may act like so:
Public method(string room){
Class Room = room;
Room.enterRoom();
}
I have already looked into using Class.forName, but all the examples were too general for me to understand how to use the function. Any help would be greatly appreciated, and if there is any other necessary information (such as more example code) I am happy to provide it.
-Sebastien
Here is the full code:
import java.awt.*;
import javax.swing.*;
public class Player extends JApplet{
public String textOnScreen;
public void start(){
room("street1");
}
public void room(String room){
if(room=="street1"){
textOnScreen=street1.enterRoom();
repaint();
}
if(room=="street2"){
textOnScreen=street2.enterRoom();
repaint();
}
}
public void paint(Graphics g){
g.drawString(textOnScreen,5,15);
}
}
public abstract class street1
{
private static String textToScreen;
public static String enterRoom(){
textToScreen = "You are on a street running from North to South.";
return textToScreen;
}
}
public abstract class street2
{
private static String textToScreen;
public static String enterRoom(){
textToScreen = "You are on another street.";
return textToScreen;
}
}

Seeing as you are rather new to programming, I would recommend starting with some programs that are simpler than a full-fledged adventure game. You still haven't fully grasped some of the fundamentals of the Java syntax. Take, for example, the HelloWorld program:
public class HelloWorld {
public static void main(String[] args) {
String output = "Hello World!"
System.out.println(output);
}
}
Notice that public is lowercased. Public with a capital P is not the same as public.
Also notice that the String class has a capital S.* Again, capitalization matters, so string is not the same as String.
In addition, note that I didn't have to use String string = new String("string"). You can use String string = "string". This syntax runs faster and is easier to read.
When testing for string equality, you need to use String.equals instead of ==. This is because a == b checks for object equality (i.e. a and b occupy the same spot in memory) and stringOne.equals(stringTwo) checks to see if stringOne has the same characters in the same order as stringTwo regardless of where they are in memory.
Now, as for your question, I would recommend using either an Enum or a Map to keep track of which object to use.
For example:
public class Tester {
public enum Location {
ROOM_A("Room A", "You are going into Room A"),
ROOM_B("Room B", "You are going into Room B"),
OUTSIDE("Outside", "You are going outside");
private final String name;
private final String actionText;
private Location(String name, String actionText) {
this.name = name;
this.actionText = actionText;
}
public String getActionText() {
return this.actionText;
}
public String getName() {
return this.name;
}
public static Location findByName(String name) {
name = name.toUpperCase().replaceAll("\\s+", "_");
try {
return Enum.valueOf(Location.class, name);
} catch (IllegalArgumentException e) {
return null;
}
}
}
private Location currentLocation;
public void changeLocation(String locationName) {
Location location = Location.findByName(locationName);
if (location == null) {
System.out.println("Unknown room: " + locationName);
} else if (currentLocation != null && currentLocation.equals(location)) {
System.out.println("Already in room " + location.getName());
} else {
System.out.println(location.getActionText());
currentLocation = location;
}
}
public static void main(String[] args) {
Tester tester = new Tester();
tester.changeLocation("room a");
tester.changeLocation("room b");
tester.changeLocation("room c");
tester.changeLocation("room b");
tester.changeLocation("outside");
}
}
*This is the standard way of formating Java code. Class names are PascalCased while variable names are camelCased.

String className=getClassName();//Get class name from user here
String fnName=getMethodName();//Get function name from user here
Class params[] = {};
Object paramsObj[] = {};
Class thisClass = Class.forName(className);// get the Class
Object inst = thisClass.newInstance();// get an instance
// get the method
Method fn = thisClass.getDeclaredMethod(fnName, params);
// call the method
fn.invoke(inst, paramsObj);

The comments below your question are true - your code is very rough.
Anyway, if you have a method like
public void doSomething(String str) {
if (str.equals("whatever")) {
// do something
}
}
Then call it like
doSomething("whatever");

In Java, many classes have attributes, and you can and will often have multiple instances from the same class.
How would you identify which is which by name?
For example
class Room {
List<Monster> monsters = new ArrayList <Monster> ();
public Room (int monstercount) {
for (int i = 0; i < monstercount; ++i)
monsters.add (new Monster ());
}
// ...
}
Monsters can have attributes, and if one of them is dead, you can identify it more easily if you don't handle everything in Strings.