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]...
I am trying to implement the following example to override the equality and hashCode method if the class has reference type member. I do get the expected result "true" for equal and "false" for non-equal objects. But the print statement in the Circle's equal method is not executed when the objects values are not equal. I don't know what i am missing, though i get the equality result "false" as expected for non equal objects.
class Point{
private int x, y;
Point (int x, int y) {
this.x =x;
this.y = y;
[code]....
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]....
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]....
I read this tutorial about overriding equal and hashcode method. [URL] ....
I understand how to override equal method, by overriding it, We can custom our compare. I also understand How to override hashcode, To make custom hash.
But still I can not understand why we do it? why if equal method override, we must override hashcode method too?If we don't what is the problem?
To honor the above contract we should always override hashCode() method whenever we override equals() method. If not, what will happen? If we use hashtables in our application, it will not behave as expected. As the hashCode is used in determining the equality of values stored, it will not return the right corresponding value for a key.
Is it the right reason in order to override:
Because when we customize equal method so it focus on special variables,We must change the hash code too in order to match with it, so hashcode also focus on those special variable.
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.
View Replies View RelatedIn 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..??
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 ?
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]....
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.
Its that very old question regarding hashcode and equals implementation which i am not getting .
import java.util.*;
public class MyElement {
public static void main(String a[]){
HashSet<Price> lhm = new HashSet<Price>();
lhm.add(new Price("Banana", 20));
lhm.add(new Price("Apple", 40));
[Code] .....
In the above program even if i comment out the Hashcode method , i believe it is still taking the memory address values from the native hashcode method of Object class. but the equals override implentation says that i have two insertions which are same . So as per my logic it should not allow the duplicate element to enter.but its not so ...the duplicate element is well inserted without hashcode .
The assignment goes like this...Write a Payroll class that uses the following arrays as fields:
employeeID - An array of seven integers to hold employee identification numbers. The array should be initialized with the following numbers:
5658845452012578951228777541
845127713028507580489
hours - An array of seven integers to hold the number of hours worked by each employee.payRate - An array of seven doubles to hold each employee's hourly pay rate.wages - An array of seven doubles to hold each employee's gross wages.The class should relate the data in each array through the subscripts.
For example, the number in element 0 of the hours array should be the number of hours worked by the employee whose identification number is stored in element 0 of the employeeID array. That same employee's pay rate should be stored in element 0 of the payRate array. In addition to the appropriate accessor and mutator methods, the class should have a method that accepts an employee's identification number as an argument and returns the gross pay for that employee.Demonstrate the class in a complete program that displays each employee number and asks the user to enter that employee's hours and pay rate. It should then display each employee's identification number and gross wages.Input Validation: Do not accept negative values for hours or numbers less than 6.0 for a pay rate.
My problem with this program is that everytime I try to print the employee ID's or the wages, I get hashcode or something like it (#[I1a77cdc or something like that). I tried using the toString method, but it lists all of the values, when I'm trying to display one at a time. Here is the code for the class:
// moduleArray class
public class moduleArray {
final int NUM_EMPLOYEES = 7;
int[] employeeID = {5658845, 4520125, 7895122, 8777541, 8451277, 1302850, 7580489};
int[] hours = new int[NUM_EMPLOYEES];
[code]...
This is the demo program to list the ID's. I've been messing with it for some time, and right now I just want it to display values.
import java.util.Scanner;
public class moduleArrayDemo {
public static void main(String[] args) {
final int NUM_EMPLOYEES = 7;
int[] ID = new int[NUM_EMPLOYEES];
[code]...
I am studying Serialization from the SCJP 6 Kathy Sierra book. I came across this code snippet.
public class Cat implements Serializable {
public static void main(String[] args) {
Cat c = new Cat();
try {
FileOutputStream fs = new FileOutputStream("testSer.ser");
ObjectOutputStream os = new ObjectOutputStream(fs);
os.writeObject(c);
[code]....
The output is as follows.
files.Cat@4d43691d
files.Cat@7f39ebdb
1) Why are the two hashcodes different?
2) Serialization is supposed to make and identical copy of any object and all its instance variables. So, if the hashcodes are different, are these objects located in different locations in heap?
Winston Gutkowski in one of the threads that one of the advatanges of String being immutable is that its hashcode could be cached. How does this work? I read somewhere that each String's hashcode is stored in a private int variable, but I don't understand how it is reused.
View Replies View RelatedI'm trying to make a method that creates objects of a parameterized type randomly, but also to store the hashCode of different objects created and if at any time the percentage of different objects is less than 50% throw an exception.
This last part is where I've gotten stuck. I have created a population property where I store the different hashCodes and update it in the method adding the new hashCode from the new object. But I don't know how to do for to know if the percentage of different objects is less than 50%.
package fp.tipos.apps;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.List;
import java.util.Random;
public class FactoriaApps {
[Code] .....
Here is my code the whole program is working correctly but the Boolean equals and the has code and it is a requirement for the assignment. Why it is not working.
I know there are issues with the code I am new with java and was struggling so I have to clean my code up before I submit the assignment but for right now I have the out put the way I want it except the Boolean and hash code methods always output that the rectangles aren't equal even when I know they are and it outputs the not equal statement twice??
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.util.Scanner;
[Code] ....
The keys in a HashMap and the values in a Set must all be unique, but this can be circumvented when using custom objects in a HashMap and Set, because the compiler has no way to determine if the objects are equal or not, as shown in the example below:
Java Code:
import java.util.LinkedHashMap;
import java.util.Map;
public class HashCodeEquals {
public void run(){
Person p1 = new Person(1, "John");
Person p2 = new Person(2, "Matt");
Person p3 = new Person(1, "John");
[code]....
Obviously the equals method is needed because that compares the two objects. But why is the hashCode method needed?
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");
[code]....
I've 3 classes.
1. Circle
2. GetInputFromUser
3. testCircle
package ABC;
public class Circle {
private double radius;
public double getRadius() {
return radius;
[Code] .....
In the testCircle class, in the line: getRadius = ui1.GetInput();
It's showing the error: The method GetInput(float) in the type GetInputFromUser is not applicable for the arguments ()
And when I do: getRadius = ui1.GetInput(rad);
It's showing the error: rad cannot be resolved
I am just trying to test this array, for a locker combination program that involves classes...but the array is printing out the whacky numbers for the location. When I try to call the method in the main, it does not work. How do I call a method that exist within a class into the main method?
public class locker {
public static void main(String[] args) {
CombinationLock();
[code]....
I am trying to call a private method to another method that are located in the same class.
I am trying to call prepareString to the encode method below.
Java Code:
public class ShiftEncoderDecoder
private String prepareString(String plainText)
{
String preparedString = "";
for(int i = 0 ; i < plainText.length();i++)
if(Character.isAlphabetic(plainText.charAt(i)))
[Code] .....
I am currently working on a dice game. I have a private method called rollDice and it performs the action of rolling two dice. For my project, I need to create another method called playerRolls and I am supposed to invoke the rollDice method in the playerRolls method and perform actions based off of that. My question right now is how do I invoke a method into another method of the same class?
View Replies View Relatedi am having a problem while calling a method..i am having a class
Java Code:
public class MySer implements Runnable {
public void getMessage(String msg)
{
...,
}..,
} mh_sh_highlight_all('java');
i use the above class in another class
[code]....
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.
[Code] ......
Im writing a simple program to understand classes and objects. Basically what I have is a file called Program.java where I have my main method.I have another file called Person.java which I want to use to create Person objects. That person can have a name, email adress, phone number, etc.I put both these files in the same folder.in Program.java my first statement is:
Java Code: import Person.java mh_sh_highlight_all('java');
My problem is that when I compile Program.java i get an error message saying that the package Person.java does not exist.So my question is, when you create a class that you want to use for objects, how do you import that class into your class with the main method so that you can use instances of your other class?
// Add range to Vehicle.
class Vehicle {
int passengers; // number of passengers
int fuelcap; // fuel capacity in gallons
int mpg; // fuel consumption in miles per gallon
// Display the range.
void range() {
System.out.println("Range is " + fuelcap * mpg);
[Code] ....
I'm compiling it in Eclipse and this continues to show in the console display
Minivan can carry 7. Exception in thread "main" java.lang.NoSuchMethodError: Vehicle.range()V
at AddMeth.main(AddMeth.java:34)