I know that System is a final class and it cannot be instantiated, out is a static final variable of type PrintStream in System class and println is a method in PrintStream class.Still I don't understand why we use System.out to call println() method.To my knowledge a method can be called using an object reference, in case of static behaviors we use classname. Then why here we are using System.out.println? Can't we just create an object of PrintStream class and call the println() method as PrintStream class can be instantiated.Are there any ways of calling a method apart from those I know(I have mentioned above what I know)?
I want to write formatted output on a notepad file using ObjectOutputStream but I am not getting it in human readable formatted form
Here is my person class
public class Person implements Serializable { private String firstName; private String lastName; private int age; public String getFirstName() { return firstName;
[code]....
I want to know how to use printStream.print() like method to write formatted output.
My problem: Every time a new account is created all previous accounts will be deleted because I use: u.println(""); and p.println(""); How can I fix this problem?
How to create object for "class B" and call the "function_B" from other different class D where class D has no connection with class A? Here is my program.
public class A(){ void print(){} } class B{ void function_B(){} } class C{ void function_C(){} }
Here, A, B, C are in the same package. But class D is in different package.
Design a class named Person and its two subclasses named Student and Employee. Make Faculty and Staff subclasses of Employee. There is also a MyDate class as explained below. A person has a name, address, phone number, and email address. A student has a status (freshman, sophomore, junior, or senior). Define the status as an integer which can have the value 0 (for "Freshman"),
1 (for "Sophomore"), 2 (for "Junior"), and 3 (for "Senior"),
but don't allow the status to be set to any other values. An employee has an office, salary, and dateHired. The dateHired is a MyDate field, which contains the fields: year, month, and day. The MyDate class does not explicitly inherit from any class, and it should have a no-arg constructor that sets the year, month, and day to the current year, month, and day. The MyDate class should also have a three-argument constructor that gets three int arguments for the year, month and day to set the year, month and day.
A faculty member has office hours and a rank. Define the rank as a String (for values like "Professor" or "Instructor"). A staff member has a title, which is also a String. Use data types for the fields as specified, or where one is not specified, use a data type that is appropriate for the particular field. Write a test program called TestEveryone.java that creates a Person, Student, Employee, Faculty, and Staff object, and invoke their toString() method (you don't need to call the objects' toString() method explicitly).
Note: Your MyDate.java class is the object class that your dateHired field is created from in the Employee.java class.
Do not use the Person, Employee or Faculty classes defined on pages 383 and 384 of the book. Create new ones.Here is the code I have so far concerning the employee and MyDate.
public class Employee extends Person { private String office; private double salary; //private MyDate dateHired; //7 argument constructor for employee public Employee(String name, String phoneNumber, String email, String address, String office, double salary /*MyDate dateHired*/) { super(name, phoneNumber, email, address);
I'm curious why ACM isn't letting me create an object from a different class, maybe I am missing something?
my main class:
import java.awt.Color; import acm.program.*; import acm.graphics.*; public class MyClass extends GraphicsProgram { private static final int WINDOW_W = 500; private static final int WINDOW_H = 500;
[code]....
I have also noticed when trying to extend 'ConsoleProgram' it does the same thing with line printing (except when using system.out).
I've been writing classes over and over for school. So I create a class outside of my main class. I create a new constructor and then create objects from my main class. I hope that makes sense. So i use methods in that class to work with the object. So I have an object name I've created <dot> method name. So I can create objects and then use methods from the class, but I'm wondering can I create a method in my main class and use it on that object? I don't understand how to do that.
I have a class of Date with a constructor with 3 parameters in it. Those 3 parameters are int data type just to enter month, year, day.
I have another class called Author which has a constructor of Date diedDate; as a parameter passing to the Author constructor.
I was asked to call the Date parameter is null, call the default constructor but I thought for the Date parameter I could only enter something like 0,0,0 instead of typing in null, null, null because null is for String data type isn't it?
Task:The main method of the class Things below creates an object called printer deriving from the class PrintingClass and uses that object to print text. Your task is to write the PrintingClass class.
Program to complete: import java.util.Scanner; public class Things { public static void main(String args[]) { String characterString; Scanner reader = new Scanner(System.in); PrintingClass printer = new PrintingClass(); System.out.print("Type in the character string for printing: "); characterString = reader.nextLine(); printer.Print(characterString); } }
// Write the missing class here
Note: In this exercise the solution is part of a conversion unit where many classes have been declared. Because of this the classes are not declared as public using the public attribute.
Example output
Type in the character string for printing: John Doe
John Doe
My Class: class PrintingClass { public void print(){ System.out.println(characterString); } }
Assuming that we have two classes B and C which inherit from class A. What is the best way to pass a parameter from an object of class B to an object of class C by the use of class A without using static variable and without defining a get function in B?
In the class below I'm trying to create a class that will accept dates in various formats and create a range. The first constructor is easy because I send it the begin date and end date as Date objects. Now I want to send a month(and year) in a constructor and derive the begin and end dates from it. In my constructor that accepts the month/year I need to put the this(startDate, endDate) at the top to be allowed, but the parameters are not built yet.
package com.scg.athrowaway; import java.util.Calendar; import java.util.Date; public class DateRange { private Date startDate; private Date endDate;
I am trying to understand Life time of a variable by writing a below program. But unable to compile it as it is throwing some error. Code snippet and error as follows,
// Understanding Lifetime of a variable. class LifeTime { public static void main(String args[]) { int x; for(x = 0; x <3 ; x++) { int y = -1; // y is initialized each time block is entered
[Code] .....
Please refer to the print screen attached 'LifeTime.jpeg' to this thread to know more about error.
I have a JavaFX application with multiple scenes. In the application one scene plays the "master" role and the others are loaded according to actions . The issue i have is that i need to redirect all the PrintStream activity to a specific TextArea on the "master" scene, and by "all" i am meaning every PrintStream activity on every scene should be redirected to this specific TextArea . The code i am using on the "master" is :
Node node =primaryStage.getScene().lookup("#ShowInfo"); TextArea ta =(TextArea)node; FXConsole console = FXConsole.getInstance(ta); PrintStream ps = new PrintStream(console, true); System.setOut(ps); System.setErr(ps); System.out.println("Test");
I am using the Singleton pattern for the rest of the scenes :
"You might wonder what happens when a static synchronized method is invoked, since a static method is associated with a class, not an object. In this case, the thread acquires the intrinsic lock for the Class object associated with the class. "What is a Class object associated with a class. Google search rather finds material about the Object class.
I have a JavaFX application with multiple scenes. In this applications one scene plays the role of "master" role and the others are loaded according to actions on the "master" scene(buttons,menu items)
The issue is that i need to redirect all the PrintStream activity to a specific TextArea on the "master" scene...
So everything that normally goes to the console to get redirected to that specific TextArea and this should be global,on every scene that is outputting something it should displayed on the specific TextArea on the "master" scene
The code i am using right now on the "master" scene is :
Node node =primaryStage.getScene().lookup("#ShowInfo"); TextArea ta =(TextArea)node; FXConsole console = FXConsole.getInstance(ta); PrintStream ps = new PrintStream(console, true); System.setOut(ps); System.setErr(ps); System.out.println("Test");
For the rest of the scenes i am using the Singleton Pattern to keep the pointing to the Specific TextArea
I want to know is there any way we can call parent class method using child class object without using super keyword in class B in the following program like we can do in c++ by using scoop resolution operator
class A{ public void hello(){ System.out.println("hello"); } } class B extends A{ public void hello(){ //super.hello(); System.out.println("hello1");
I am a beginner here at JAVA and I am trying to program a Gratuity Calculator using both interface class and object class but it keeps on compiling with errors saying "cannot find symbol".I tried everything to fix it but it just keeps on stating symbol.
[CODE] public class GratuityCalculator extends JFrame { /* declarations */
// color objects Color black = new Color(0, 0, 0); Color white = new Color(255, 255, 255); Color light_gray = new Color(192, 192, 192);
In the process of creating a new class, I need to move my main method from the class SaveDate to the class DynamicTest. Below I have listed the code of both classes.The objective is to be able to run my program from the DynamicTest Class. I need understanding the process of moving my main method to a different class and creating an Object of a class and calling its method.
public class SaveData { private static final Map<String, Object> myCachedTreeMap = new TreeMap<String, Object>(); public static final List<String> getLines(final String resourceParam, final Charset charset) throws IOException{ System.out.println("Please get: "+resourceParam); if (myCachedTreeMap.containsKey(resourceParam) ) { // Use the cached file, to prevent an additional read.
The assignment is to create a SmartString class that implements a SmartStringInterface class (created by professor) and implements a few methods. We are basically taking a string and then taking various substrings and inserting, deleting them and undoing changes as well. Here are the methods in the interface to use along with the parameters.
public interface SmartStringInterface { public void insert(int pos, String sstring); public void delete(int pos, int count); public void undo(); public String toString();
The Undo is supposed to be able to be called multiple times (to be tested using a driver program that we must create) but the part that's got me is that the changes are only supposed to be stored. Currently, I am storing the "new" string after each change onto a stack, so that undo can just pop off the stack and it will revert to the previous string. Professor said that was wrong, so I don't know how to do it. Here is what I have so far (some of the code we have is using default StackADT stuff from our book, so if you need that I can post as well. You can see in the undo method where I currently save the string. We can use multiple stacks if needed, but the less the better. Must use at least 1. The exception code is already coded for us in another file also. I am only having to code these methods and the driver to test.
import java.util.Arrays; public class ArrayStack<T> implements StackADT<T> private final static int DEFAULT_CAPACITY = 100 private int top; private T[] stack;
how objects relate to classes and how you can create and re-use object types.on that point, but this has me baffled. I most certainly do not have a firm grasp yet on passing things to and from methods that just makes my head hurt. SO anyway I tried out one of the code examples:
/* ElectricGuitar.java */ class ElectricGuitar { String brand; int numOfPickups; boolean rockStarUsesIt;
[code]...
But I just realized this thing has no main method and only one class defined.....so I guess I just tried to compile.
