Does Java Extend 2 Classes At One Time
Feb 7, 2014
1) when you create a class and compile it and open and see the class using javap command .. that class file contains that it extends java.lang.object and a default constructor is created automatically..... But when you extends another class the java.lang.Object class is not appeared as extended why?
Code example:
1St Case ----- Java code:
public class temp(){
}
Javap Code:
public class temp() extends java.lang.Object {
public temp(){
}
}
2nd case --- Java Code:
public class temp() extends dummy{
}
javap Code:
public class temp() extends dummy{
public temp(){
}
}
why for the above scenario it doesn't extends object class .. if it does implicitly then why it did not do in the first case instead why did the compiler extends Object class ?
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May 16, 2014
Can an interface extend a class?When I am running the following code it's showing some errors..I have commented them.
class A {
public void methodA() {
System.out.println("Class A methodA");
}
}
interface B extends A //interface expected here {
public void methodA();
[code]....
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Apr 27, 2015
I have a checksum function that is suppose to read IPV4 packet and return a short integer value. The IPV4 packets are stored in a byte array. I am having trouble storing the first 8 bits and second 8 bits of the short integer into the byte arrays especially when they have leading 1s. For example, if my checksum returns 5571 (binary = 0001 0101 1100 0011) The first 8 bits is suppose to represent 195 but when I try to assign a larger integer type to a btye the information gets sign extended. The 195 turns into -61. I tried using bit addition like array[10] = array[10] & 0xff, but the result remains the same.
public static short checksum(byte [] a, int length) {
short sum = 0;
long data;
int i = 0;
while(length > 1) {
data = (((a[i] << 8) & 0xff00) | ((a[i + 1]) & 0xff));
sum += data;
[code]....
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Apr 12, 2014
how to 'implement' an interface and 'extend' a class. Now I want to try and recall the information by memory without using any reference material.
Implementing an interface...
Java Code: //This interface will hold information for cell phones//Like saying... you can't BE a cell phone unless you have this information, at the very least
public interface CellInfo {
public void model();
public void make();
public void androidVer();
}
//Now I implement the interface for a class called Galaxy, which is a class about a specific phone
public class Galaxy implements CellInfo
public void model() {
System.out.println("I'm a Galaxy S5.");
}
public void make() {
System.out.println("I'm made by Samsung.");
[code]....
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Jul 18, 2014
I have a GUI that I've been working on for a while now. What I am trying to figure out, is a way to have the user push a button, and when they do have the GUI extend out to the right with another table to use for Filter Data. Once They are done, I want them to push that button again, and the panel with the query data retracts and is hidden again, all without changing the size of the current GUI in question. I've tried a bunch of different things with setting preferred and Minimal values to my GUI, and I've played around with different Layouts (Border Layout.East, etc), but I can't seem to find a good working solution.
Ideally it would be slick if I could make my panel SLIDE out and SLIDE back in, which would look really cool, but I'd settle for something that just worked.
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Nov 3, 2014
I want to extend hashCode method in my class. As we know that hashCode is generating with 32 bit. Now I wanna generate 64-bit hashCode for user given Input.. Input may be string or Integer.
Please let me know.. take me out from this problem..
MY code follows like this...
package hash_table;
public class Hash_table
{
private int num;
private String data;
public boolean equals(Object obj)
{
if(this == obj)
[Code]...
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Feb 4, 2014
I am working with a program where I am required to use a JFrame in a child class. The only way that I know how to access a JFrame is to do, example (public class Example extends JFrame), but since it is already extending the parent class, I am kind of stuck. I do not think that you can extend two separate classes, so..... I am stuck.
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Jun 22, 2014
In the following program i have called the anonymous class of dev class.
interface emp {
void desig();
}
public class dev implements emp {
dev e = new dev() //this line is throwing error ...works fine if i use emp instead of dev {
[Code] .....
i am getting stack over flow error as :
Exception in thread "main" java.lang.StackOverflowError
at dev$1.<init>(dev.java:17)
at dev.<init>(dev.java:16)
at dev$1.<init>(dev.java:17)
[Code] .....
Is it because the jvm is not able to decide which of the 2 desigs() it has to load in the memory when its object is created in the main..??
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Apr 9, 2015
I've written a java application with several classes all in the same .java file. It works just fine. Now, I've broken it up so that each class has its own .java file. Still works fine. My next step is to put those classes into a package, but I'm not about to get the program to run.The .java source files are all in /home/user/src
I've set the CLASSPATH to /home/user/src..All of the source files have "package com.myfirm.program" on the first line.I compiled the application with:
javac -d . File1.java File2.java File3.java (etc...)
the compiler created the directory: /home/user/src/com/myfirm/program and put all of the .class files in there.So how do I get the program to run? if I run from /home/usr/src
java File1
I get: Exception in thread "main" java.lang.NoClassDefFoundError: File1 (wrong name: com/myfirm/program/Program)
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Jan 19, 2015
Wondering, what is exactly reason for existence of inner classes? Are there problems that without them you can not resolve?
Anything beside emulate multiple inheritance - when your class need to extends the real classes, and not implement multiple interfaces ?
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Jan 19, 2015
What is exactly reason for existence of inner classes? Are there problems that without them you can not (or be very hard to) resolve? Anything beside emulate multiple inheritance, when you need to extends the real classes ( not implements multiple interfaces) ?
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Jun 4, 2014
why don't I define my methods in a class, rather than going a level up and declaring it first in an abstract class/interface? If the point is to have different implementations for different needs, then we have the option to override the methods.
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Aug 19, 2014
I was wondering how Java knows where to Import classes from when we don't specify the whole directory path.
For example: import java.util.* Does It automatically search In both your current directory and the directory created during Installation that contains the standard library (wherever It may have been Installed) ?
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Apr 1, 2015
Consider the two simple Java classes below:
Java Code:
class Computer {
Computer() {
System.out.println("Constructor of Computer class.");
}
void On() {
System.out.println("PC turning on...");
}
void working() {
[Code] ....
After the program run, how do I trace (1) which object call which method (2) and how many times?
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Aug 16, 2014
I studied that java does not support multiple inheritance using classes. It is fine practically, but I have still a question in mind:Lets see the below code.
class Test{
------
------
}
class MyTest extends Test{
---------
---------
}
Here, as we know that that Object is Super class for every class in java. and I have already extends a Test class in MyTest.My question is: How is it possible to extend features of two class at the same time?
Theoretically,
MyTest extends Object &
MyTest extends Test.
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Feb 9, 2015
I am working on an assignment that I can't seem to figure out the final part to. The program takes in course data such as the time the class starts and how long it lasts. The time is in military time (0000 - 2400)
I need the output time to be the time the class started, plus the length of the class, and displayed in military time.
for example,
Start Time = 0930
Length = 50 minutes
Endtime = 1020
I can't for the life of me figure out how to do this. I have gotten a program that works for this time and minutes, and displays the correct 1020. But when I change the information to say
Start time: 0700
Length = 90 minutes
I get:
Endtime = 90
90 is technically correct, the way the formula is setup, but I need it to display 0900 not 90.
Here is the code that I have. Be easy, I'm still learning, and this is just the file I created to get the formula to work. Also, the verbose in here is just for my own debugging to make sure values should be what I'm expecting them to be.
public class calc
{
public static void main(String[] args) {
double hours, minutes, length;
double temp;
int time = 2400;
hours = time / 100;
System.out.println("Hours are: " + hours);
[Code] ....
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Jul 3, 2014
I have two string representations of time in "HH:MM:SS" and I want to minus one time from the other.
For example if a = 10:20:30 and b = 00:50:20, i would get 09:30:10. What is the best way to do this?
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Jun 28, 2014
I work as a golf staff I would like to create application which would tell me the playing time and the time when players need to reach certain playing field/hole. my ideas is to make a program which would ask the user to input their starting time and than select the hole number, where the end result would be amount of actuall time.
I have been having hard time to figure out howe to properly structure the input conversion so it is recognized as a time (Exampke: 10:15). Do I need to use the calendar method in Java or ?
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Jun 1, 2014
I just want to calculate search time for my algorithm . How to get system time in java other than System.nanotime() and System.currenttimemillis() as these methods does not returns consistent time for same input is their another option to get system time???
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Oct 22, 2014
My program is working fine. When I executes it, it shows me this:
The clock is 54 minutes over 23 (+41 seconds.
and when i press ENTER, it shows me this:
23:54:41
But then it won't show me the update. I want to update the time, for example when I started the execution the time was 23:54:41 but it must show me something like 23:54:45, because I need the current time.
I have searched the whole internet about this but I don't know how to use the "Date.update ();".
Here is my code
package p2;
import java.util.Calendar;
import java.util.Date;
import javax.swing.JOptionPane;
public class Time {
public void myTime() {
Calendar cal = Calendar.getInstance();
[Code] ....
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Apr 13, 2014
We can specify the start date & time using timer class. any option to provide end date & time also with out using third party.
I want to run a job between two given dates at given interval gap.
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Aug 21, 2014
Is there any command to find all the classes inside a package?
E.g. : To find all the properties and methods inside a class String we use "javap java.lang.String" ....
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Mar 15, 2015
The question states: Design a class named LinearEquation
for a 2 x 2 system of linear equations:
ax + by = e
cx + dy = f
Where
x =
ed − bf/ad − bc
y =
af − ec/ad − bc
The class contains:
- Private data fields a, b, c, d, e, and f.
- A constructor with the arguments for a, b, c, d, e, and f.
- Six get methods for a, b, c, d, e, and f.
- A method named isSolvable() that returns true if ad−bc is not 0.
- Methods getX() and getY() that return the solution for the equation.
Write a test program that prompts the user to enter a, b, c, d, e, and f and displays the result. If ad − bc is 0, report that "The equation has no solution."
I believe that my program is correct because I am able to compile it and get no errors, however I have no clue how to display the information for x and y or display this equation has no solution if ad-bc=0.
Java Code:
import java.util.Scanner;
public class Exer911 {
public static void main(String[] args){
// Create a scanner system to hold the numbers for each variable
Scanner input = new Scanner(System.in);
// Prompt the user to enter a number for each of the variables
[Code] ....
How to get the information to display ....
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Nov 16, 2014
I'm trying to write a program the simulates the time delay of an elevator door and I want to know how I can add an interactive time in delay in Java.
I know that this is how you delay a Java program:
try {
Thread.sleep(60000);
}
catch(InterruptedException ex) {
}
But how can I make it so that the user can make the timer last longer or end faster through user input.
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Jan 22, 2014
What I'm doing about it: googling the shit out of my problems, consulting you fine readers, consulting my friends, and yesterday I signed up for Lynda.com. I'm hoping 30hrs+ or so of watching, rewatching, and analyzing the example code will catch me up before I get too behind in CS302
** Assignment Prompt **
Integer types are very convenient, but their limited width and precision makes them unsuitable for some applications where precision is more important than speed. Develop a class VeryLargeInteger that can handle arbitrary long integer numbers (both negative and positive) and the basic arith- metic operations (addition, subtraction, multiplication, division, and remainder).
Hint: The number could be represented as string, the sign could be represented either as boolean or as part of the string.
Note: Implementations of addition/subtraction through repeated use of a constant incremen- t/decrement will not be accepted. Implementations of multiplication and division that rely only on addition and subtraction will not be accepted.
I know I'm going to have to create a separate tester to call on the VeryLargeInteger class and it's math methods. For the new data type, should I convert the integer/string into an array in order to handle the large length of the number? I know he wants us to use recursion for the math methods. My gut tells me addition and subtraction will be slightly easier than multiplication and division. I know I'll have to reference the other methods for division. We aren't allowed to use the BigInteger class.
How I should construct any of the methods.
Java Code:
import java.util.ArrayList;
/**
∗ VeryLargeInteger (VLI) is a class for arbitrary precision integer computation
*/
public class VeryLargeInteger {
private int[] num1;
private int[] num2;
private int[] num3;
[code]....
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Jan 29, 2014
I have two classes. time_runner is used for testing my code.
This is what I'm using to test my code:
class time_runner
{
public static void main(String str[]) throws IOException {
Time time1 = new Time(14, 56);
System.out.println("time1: " + time1);
System.out.println("convert time1 to standard time: " + time1.convert());
System.out.println("time1: " + time1);
System.out.print("increment time1 five times: ");
time1.increment();
[code]....
The two constructors are "Time()", which is the default constructor that sets the time to 1200, and "Time(int h, int m)" Which says If h is between 1 and 23 inclusive, set the hour to h. Otherwise, set the hour to 0. If m is between 0 and 59 inclusive, set the minutes to m. Otherwise, set the minutes to 0. Those are my two constructors that I pretty much have down. The three methods however I'm having trouble with. The "String toString()" Returns the time as a String of length 4. The "String convert()" Returns the time as a String converted from military time to standard time. The "void increment()" Advances the time by one minute.
public class Time {
private int hour;
private int minute;
public Time(int h, int m) {
if(h > 1 && h < 23)
hour = h;
[code]....
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