How To Cast PrintStream Object In ObjectOutPutStream
Jul 10, 2014
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.
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)?
Im trying to loop through a hashmap of objects. They are defined as People objects. People has two subclasses , Instructor and Student. As I am looping through the map of People, I am searching for class Instructor. If I find it, I want to access its method getDepartment in a println by casting to Instructor. When I do I get a runtime error:
Exception in thread "main" java.lang.ClassCastException: java.util.HashMap$Node cannot be cast to uStaff.Instructor at uStaff.PersonApp.menu(PersonApp.java:108) at uStaff.PersonApp.main(PersonApp.java:21)
//Instantiate the different Person, student and instructor objects Person thisPerson = new Person(01,fName,mName,lName,email,ssn,age); Student thisStudent = new Student(02,"Stacey","Marie","Morgan","smorgan@gmail.com","213-45-6789",20); thisStudent.setMajor("music"); Instructor thisInstructor = new Instructor(03,"Joe","Douglass","Wells","joe@drumhaven.com","555-98-3029",46); thisInstructor.setDepartment("Computer Science");
I'm developing an application to track the status of a production flow-line and have hit a bit of a snag. When attempting to read saved data I run into this:
Exception in thread "main" java.lang.ClassCastException: flowline.End_Of_File cannot be cast to flowline.Operation at flowline.Station.checkLoadPreviousStationStatus(Station.java:91) at flowline.Station.main(Station.java:212) Java Result: 1
I've been reading up on different methods to saving and retrieving data and have decided ObjectInputStream would be the best option.
The save method works fine, I opted to use a EndOfFile class to determine when I've reached the end of the input stream. The problem is, when my loop encounters this object, it doesn't terminate the loop.
public void checkLoadPreviousStationStatus() throws FileNotFoundException, IOException, ClassNotFoundException, EOFException, TempArrayOutOfBoundsException{ Object loadOpn = null; End_Of_File eof = new End_Of_File(); File f = new File(fileName);
[Code] .....
The Operation cast is a cast to the objects my LinkedList contains. The highlighted line is where the exception occurs.
I am getting "Type safety: Unchecked cast from Object to LinkedList<EventData>" in eclipse for a piece of code stated below
public LinkedList<EventData> loadFromFile(File file) { queue=new LinkedList<EventData>(); //Some piece of code return (LinkedList<EventData>)queue.clone(); //--->getting warning here }
I know that because clone() method is returning Object, hence compiler doesn't have type information that's why showing warning. I don't want to suppress this warning instead i want to fix it.
My assignment is to create an ObjectOutputStream object mapped to a binary output file named "ItemRecord_binary.txt". So far I've created a ItemRecord class with a constructor with getters and setters and a override toString method. It compiled. This ItemRecordReport class does not compile because of a can't find symbol error. Here is the code:
import java.io.*; import java.io.IOException; import java.io.ObjectOutputStream; import java.util.Scanner; public class ItemRecordReport { private ObjectOutputStream output;
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 :
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?
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 ve got a 2d array and I want to cast it in an 2d arraylist. I ve create a function that cast an array to arraylist. My problem arises, when I tried to parse the whole 2d matrix to the arraylist. I use the following code:
Java Code: double sums[][] = computeSums(lab, projections); ArrayList<ArrayList<Double>> lists = new ArrayList<ArrayList<Double>>(); ArrayList<Double> nu = new ArrayList<Double>(); System.out.println(sums[0].length); for (int i = 0; i < sums.length; i++) {
The problem is that only the first matrix sums[0] is copied to the 2d arraylist sums.length times. How is is possible to store all the different sums matrices to the arraylist??
I'm actually trying to complete the excersise of the Servlets and JSP book in page 303 but I'm getting the following error in Eclipse Cannot cast from String to ArrayList(JSP).Here is the code
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <%@ page import="java.util.*" %> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Hobbies Sharing</title> </head>
[code]...
The error as it appears in line <% ArrayList al = (ArrayList)request.getParameter("Names"); %>
When does an internal cast actually happen? I am aware that compound assignment operator do an internal cast. Does it happen in Assignment 1?Assignment 2?Assignment 3?Assignment 4?
Java Code:
public class Parser{ public static void main( String[] args){ byte b=1; short s=1; int i=1; s=b;//Assignment 1 s<<=b;//Assignment 2 b<<=s;//Assignment 3 s +=i;//Assignment 4 } } mh_sh_highlight_all('java');
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Boolean at javax.swing.plaf.synth.SynthTableUI$SynthBooleanTa bleCellRenderer.getTableCellRendererComponent(Synt hTableUI.java:731) at javax.swing.JTable.prepareRenderer(JTable.java:573 1) at javax.swing.plaf.synth.SynthTableUI.paintCell(Synt hTableUI.java:684)
I am working on a program where I want the user to input multiple classes.
One int, and one String.
Can this be done? if so, how?
I have a tried to get input from both, like in the code below:
Java Code:
import java.util.Scanner; public class ForumFlowchart { public static void main(String[]args){ //Creating scanner. Scanner input = new Scanner(System.in); //Get information about job System.out.println("Type in Int"); int i1 = input.nextInt();
[Code] ....
If I keep my input in the same class, I get the error "Can not cast int to string". My question is, it is possible to get an input from both an Int and a String in the same program?
I have a msg object that contains an ArrayList<Integer> collection. However, in order to send the elements in the array over the udp socket, it needs to be sent as a byte[] array. So why am I using ArrayList<Integer> over byte array in first place? Well when I receive data from socket from embedded c program, I need to get an unsigned representation of the data, and thus I need to store it in integers, since bytes in Java are unsigned and unsigned chars in c that are greater than 127 will yield incorrect values in java. But when I send an ack back over the socket, I need to send the data back as bytes. So I convert the ArrayList<Integer> to a byte array:
Java Code: byte[] data = msg.toByteArray(); DatagramPacket response = new DatagramPacket(data, data.length, packet.getAddress(), packet.getPort()); public class Gprs { ... public byte[] toByteArray(){
[Code] ....
The problem is I get an "Cannot cast from Integer to byte" when trying to cast the integer to byte: data[i] = (byte)m_data.get(i);
Create an equals method that takes an object reference and returns true if the given object equals this object.
Hint: You'll need 'instanceof' and cast to a (Geocache)
So far I have:
public boolean equals(Object O){ if(O instanceof Geocache){ Geocache j=(Geocache) O; if (this.equals(j)) //I know this is wrong... but I can't figure it out return true; }
else return false; }
I think I have it correct up to the casting but I don't understand what I'm suppose to do with the this.equals(). Also I'm getting an error that I'm not returning a boolean... I get this all the time in other problems. I don't get why since I have to instances of returning booleans in this. "returns true if the given object equals this object" makes no sense to me. I assume the given object, in my case, is 'O'. What is 'this' object referring to?
I am new to Java and have read books, the Java docs, and searched the Internet for my problem to no avail. I have an Array of objects that contains strings. How can I get the object's strings to print in a list so that the user can select that object to manipulate its attributes? For example, the user can select "Guitar 1" from a list and manipulate its attributes like tuning it, playing it, etc. I have a class called Instruments and created 10 guitar objects.Here is the code:
Instrument [] guitar = new Instrument[10]; for (int i = 0; i < 10; i++) { guitar[0] = new Instrument("Guitar 1"); guitar[1] = new Instrument("Guitar 2"); guitar[2] = new Instrument("Guitar 3"); guitar[3] = new Instrument("Guitar 4"); guitar[4] = new Instrument("Guitar 5"); guitar[5] = new Instrument("Guitar 6");