How Many Objects Created With New String Method
May 22, 2014
I am little confused about String creation in java.
Doubt 1: How String objects assigned to Pool area:
1. String s="in pool";
2. String s1= new String("not in pool");
How many objects created in statement 1 and 2. According to recent discussion with my colleague, one object created in String pool in case 1. And in case 2, two objects are created, one as literal goes to String pool and other with new() opr goes to Heap.
If above is correct, Ain't we wasting double memory for same object ? Really need clear understanding on this
Doubt 2: How does intern() work: Please see if my below explanation is correct
1. If String literal is already present in String pool , and i create a same string with new operator, reference to object is changed to pool area.
2. If String object is created using new operator and intern is called on it. If same string object is not present in the String Pool, Its moved to String pool and reference to this in Pool is returned.
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Aug 15, 2014
how many objects got created at each line (in String pool or in Objects memory):
public class Test {
public static void main(String[] args) {
String s1 = "test";
String s2 = new("test");
String s3 = s1 + s2;
StringBuider sb = new StringBuilder().append(s2);
}
}
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Dec 9, 2014
Why query string is not getting created in doPost method of HttpServlet?Is this reason is enough - it is supplying data in html body.
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Jan 19, 2014
String s= new String ("Hello");
String a = new String ("Hello");
As per my understanding the first line creates 2 objects : 1 for the heap memory and 1 for String pool
2nd line : new object created and no new object created in the String pool as the keyword already exists in the pool.
So the total number of objects created after the execution of 2 lines are : 3
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Mar 13, 2014
Which is the best way to keep track of the number of the objects I've created?Is is a good practice to have a static variable, which will be incremented everytime I call a contructor?
Class circle{
private double x,y,radius;
private static count;
Circle(double x1, double y1, double radius1){
x=x1;y=y1;radius=radius1;
count++;
}
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Mar 11, 2015
Is it possible to have the value of an entered String to be set as the name of the String to be created whilst running.For example: String username= Keyboard.readString() & the user entered for example the word: "Hello".Is there a way how I can make the Java Program create another String named Hello (Inputted value of String username).
If this is allowed, what do I have to use and if possible show me exactly what I have to do with the example mentioned above?
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Oct 29, 2014
I am working on an independent project it is a simple little text based rpg that will run in a counsel window. I have an object for Character that is creating during a CreateCharacter method. I want the play to be able to enter a character that will open up a menu that displays things like the name and health and stuff of the character from the object created in CreateCharacter, but because I have it in a different class I don't know how to reference the object made in CreateCharacter.
I have it in 6 files
Character --- Object with getters/setters for things like name, age, race, class, ect
MainMenu --- Displays title and promts for new game and quit
CreateCharacter --- Walks through and sets all values in Character
Stats --- Keeps the players stats (health, attack, ect) in an array
Intro --- Beginning demo thing (not really important for this question)
Menu --- Displays all current user stats (Having issues with this one)
Example I have this in Menu
System.out.println("Name: " + ????.getName());
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Jan 23, 2015
how String objects are different from other objects
part 1:
// creating two objects
Dog mydog1 = new Dog();
Dog mydog2 = new Dog();
// comparing the reference variables
if( mydog1 == mydog2){
System.out.println(" The reference variables refer the same object ");
}
else {
System.out.println(" They refer to different objects ");
}
The above code works as I understand objects , it prints "They refer to different objects " to the screen.
Part - 2
// creating two objects ( I beleive, pls correct me if i am wrong )
String a = "haai";
String b = "haai";
if( a == b){
System.out.println(" Reference variables refer to same object");
When i run the above code it prints that a and b refer same object , I don't understand how they refer to same object when i didn't assign " String b = a; ". My question is did java just create one object and stored the same reference values to a and b .
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Mar 26, 2014
I have to create a class that has two fields. One called length and the other width. I have to make a method that returns the tract area. Similarly, I also have to make a method that indicates whether two objects have the same fields. Here is the code that I have assembled...so far
// create private fields to hold width and length
private double width;
private double length;
[Code].....
My problem is encountered when writing that equals method
if(length.equals(object.length) && width.equals(object.width))
I get an error saying HTML Code: cannot invoke equals(double) on the primitive type double. Meanwhile, I do see, to realize that when I change my fields to capital "Double." The problem disappears; however, in my class I have never dealt with a situation where I have to use capital d in double. In fact, I don't even know what's the difference between Double and double. I do know what double is but not the other one..
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Nov 22, 2014
I want to loop through each of my objects and call the method for each one. ( polymorphic array )
Error: Constructor Dog in class Dog cannot applied for gives Types
Required String,String
Found: no arguments
Reason actual and formal argument lists differ in length
Java Code:
public class animal {
private String m_type="";
private String m_name="";
public static void main (String[] args) {
[Code] ....
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Nov 7, 2014
How can I write a method that takes a string with duplicates letters and returns the same string which does not contain duplicates. For example, if you pass it radar, it will return rad. Also i would like to know how can I Write a method that takes as parameters the secret word and the good guesses and returns a string that is the secretword but has dashes in the places where the player has not yet guessed that letter. For example, if the secret word is radar and the player has already guessed the good guesses letters r and d, the method will return r-d-r.
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Sep 27, 2014
I am currently trying to make a calculator in Java. I want to use the String split method to tokenize the string of characters inputted. I thought I was using the String split method wrongly, because I had surrounded the characters I wanted to delimit with square brackets. However, when I removed the square brackets, the code threw an exception when I pressed the equal button. The exception was a PatternSyntaxException exception. Am I using the String split method wrongly? And why is the exception thrown? Here is my code:
import javax.swing.*;//import the packages needed for gui
import java.awt.*;
import java.awt.event.*;
import java.util.Arrays;
import java.util.List;
import static java.lang.Math.*;
public class CalculatorCopy {
public static void main(String[] args) {
[Code] .....
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Dec 16, 2014
i am trying to write a class method which will take in a string and returns a string which is the reversed version of that string. it compiles fine but when i try to run it it states Main method not found in class StringReverse,please define the main method as public static void main(String[]args). I am new to java and cannot figure out
import javax.swing.JOptionPane;
public class StringReverse {
public String reverseString(String str){
JOptionPane.showInputDialog(null,"Please enter word");
char c = str.charAt(str.length()-1);
if(str.length() == 1) return Character.toString(c);
return c + reverseString(str.substring(0,str.length()-1));}}
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Apr 20, 2015
I have application written in rest with Jersey-Jackson for JSON processing. All the resources produce and consume JSON. Now, the problem is, it is a server intensive application and large number of request will be hitting the server with large JSON request object. Now, because of this reason, when the JSON object gets converted in to Java object with String fields in it mapping to JSON request values large number of string objects are getting created which is resulting in frequent GC.
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Apr 15, 2015
if some of you worked with Unity Game engine (C#) the idea is that game has main loop and once per cycle it call for example Update() method in all objects which implement certain interface.
I would like to repeat such pattern in Java for another another program, not even game related, but I would still need a main loop and event driven behaviour with async call backsSo question is how to implement the fallowing scenario:
Imagine i have interface which implement some methods and one of them is Execute()
I have the main controller class which implement main loop, also multiple other classes which implement the same interface with method Execute(). How can i call this Execute() method on all objects which implement that interface each loop cycle?
Should i keep and track reference of each object which was implemented with this interface and go through inner "for" loop trough each reference and call manually Execute() method in each of them?what if each object implementing interface have to run Execute() method simultaneously? in parallel independent from each other?
Referring back to Unity engine and their Update() method - there is exactly the same situation:you can have multiple objects with script attached, thats script implement interface which has multiple methods and one of them is Update() and once per cycle all objects with that Update() method will be executed in parallel independently
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Jan 28, 2015
I want to clarify it whether this below code, when running this loop, will it create separate string objects as strings are immutable or else, will it keep the same reference(as each time inside loop, we use the same name 'rslt') and assign new string value for this?
while(inc < numberOfColumns){
String rslt=rs.getString(inc+1);
rowArr[inc] = rslt;
inc++;
}
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Apr 4, 2015
This is what I have to create : Write a method that returns the largest object in an array of objects. The method signature is:
public static Object max(java.lang.Comparable[] a)
All the objects are instances of the java.lang.Comparable interface. The order of the objects in the array is determined using the compareTo method.
Write a test program in the main method that creates an array of ten Strings, an array of ten Integers, and an array of ten java.util.Dates, and finds the largest string (i.e. in the alphabetical order), Integer, and Date in the arrays.
Name your java class Max and your java file Max.java.
I am struggling a bit with this code as I am sure you can see, and am at loss. I have never used the compareTo method. Am I doing this right, or on the right track with my code?
public class Max implements Comparable {
public static Object max(java.lang.Comparable[] a) {
java.lang.Comparable tempObj = null;
for (int i = 0; i < a.length; i++) {
if (a[i].compareTo(tempObj) > 0)
[Code] ....
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Jun 14, 2014
Say I have two classes, Author and Book, and I have 2 author objects and 10 book objects. I would like to know how to do two things:
1) Make some sort of connection that makes clear that author X wrote books A, B and F.
2) Call a method from a book object that is connected to an author.
Seeing as I don't know which books will be connected to an author, is there some way to call a method of an object bases on a variable object name? Something like call the getFirstPage() method for every book that is linked to author X?
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Apr 8, 2014
I have a school assignment that involves me sorting an array of objects based on one of the class String variables. I am using as the title says a simple selection sort method. The problem I'm having is that when I run the program in debug mode, it never seems to enter the if statement in the inner loop. I would like to say I've tried a number of things to figure it out, but honestly I'm just stumped as to why it's not working.
Here is the code:
public static void sortTransactions(Transaction[] oTransaction){// This is the sorting method, obviously it's not done so it currently just prints to screen.
System.out.println("Successful call to sortTransaction()");
String min = "";
int curInd = 0;
Transaction[] temp = new Transaction[1];
[Code] ....
The output when I check to see if the array is sorted verifies that the array never does get sorted.
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Mar 18, 2014
Code a Java method that accepts a String array and a String. The method should return true if the string can be found as an element of the array and false otherwise. Test your method by calling it from the main method which supplies its two parameters (no user input required). Use an array initialiser list to initialise the array you pass. Test thoroughly.
public class test {
public static void main(String[] args) {
Printhelloworld();
String[] verbs = {"go", "do", "some", "homework"};
printArrays(verbs);
[Code] .....
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Sep 21, 2014
So I'm creating a class which when given three inputs uses them as sides of a triangle and tells ther user what type of triangle it is, or if the input is invalid, tells them why it is invalid. I'm readin the input as a string and then trying to split it into a string array, from there checking to see if it has 3 elements.. in which the data is good at that point, and then converting them to ints and checking to see if they're negative ansd finally checking to see if they can work as sides of a triangle ie a+b >c, a+c >b , b+c >a.
I'm trying to split it into an array of strings but am getting an error, and can't seem to figure out why as this should be working from what I've read of the string.split method online.
import java.util.*;
public class TriangleTest{
private int sideA;
private int sideB;
private int sideC;
public static void main(String[] args){
TriangleTest triangle = new TriangleTest("3 4 5");
[Code] ....
The output reads [Ljava.lang.String;@15db9742
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Mar 7, 2014
My intention is to see the real reference values (memory locations) of 2 StringBuilder objects as below:
StringBuilder sb2 = new StringBuilder("123");
StringBuilder sb3 = sb2;
System.out.println(sb2);
System.out.println(sb3);
I was expecting a printout like
@S234853
@S984724
But all I got was 123 printed twice. How can i print out the reference values instead of what is inside the StringBuilder object ?
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May 11, 2012
I'm doubted regarding the implementation of Collections.binarySearch() method on an ArrayList of objects of a custom class Movie.
Here is the movie class :
public class Movie implements Comparable<Movie> {
String movieName;
String rating;
String director;
String theme;
[Code] .....
The sort/binarySearch in searchByMovieName function is done with natural sorting (and Comparable Interface in Movie class). I mean no comparators involved here. And the comparator that I used for sorting/binarySearching on Movies Director attribute in searchByMovieDirector function is :
public class MovieDirectorComparator implements Comparator<Movie> {
public int compare(Movie movie1, Movie movie2) {
return movie1.getDirector().compareToIgnoreCase(movie2.getDirector());
}
}
But I was not able to implement binarySearch ?? How to implement the binarySearch here. I have google to see only binarySearch working on Arrays or probably ArrayList of String only, but not on ArrayList of custom objects.
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Oct 20, 2014
The only problem I am having is I cannot get my string plainText to go through the encode and prepareString methods.
Is there something in my methods that is wrong, or is it the way that I am calling them?
What is happening is if I enter "this is a test" as a plainText I am getting the samething back with no changes.
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Aug 7, 2014
I am getting incombatable types, I do not know why I am getting them..why I am getting the error?
The Error I am getting:
stringSort.java:26: error: incompatible types
if(myArray[j].compareToIgnoreCase(myArray[i].toString())){
^
required: boolean
found: int
*/
[code]....
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Oct 23, 2014
I need to get the string encodedString from the method encode able to be used in the decode method.
Java Code:
public String encode(String plainText) {
int prepareString;
int shiftChar;
String preparedString2 = prepareString(plainText);
String encodedString = "";
for(int c = 0 ; c < preparedString2.length();c++)
[Code] ....
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