What is the difference between Java's compare() and compareTo() methods? Do those methods give same answer?
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I'm implementing compareTo() method for a simple class such as this (to be able to use Collections.sort() and other goodies offered by the Java platform):
public class Metadata implements Comparable<Metadata> {
...
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An Enum in Java implements the Comparable interface. It would have been nice to override Comparable's compareTo method, but here it's marked as final. The default natural order on ... |
Java's PriorityQueue places the least element at the head of the list, however I need it to place the greatest element at the head. What what's the neatest way ... |
I profiled my code and found out that my class, which implements Comparable<T>, spends 8x more cpu time in
compareTo(Object)
than in
compareTo(T)
I assume that the slowdown is because of virtual table ... |
Ok, I'm officially stumped on this one. I have a GregorianCalendar object that I would like to determine if it is in the past, present, or future. So far, the |
I want to make a class usable in SortedSet | SortedMap.
class MyClass implements Comparable<MyClass>{
// the only thing relevant to comparisons:
private final String name;
//...
}
The class' instances ... |
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I am building a bubble sort and I want it to be able to accept both Integer and String parameters. I cast all input as Strings and use the compareto method ... |
In the Java textbook I'm learning from, it says that this uses "lexicographic ordering" to return an integer. I understand how it works, but what is a specific way this is ... |
Is it a valid way of comparing dates:
Calendar someCalendar1 = Calendar.getInstance(); // current date/time
someCalendar1.add(Calendar.DATE, -14);
Calendar someCalendar2 = Calendar.getInstance();
someCalendar2.setTime(someDate); // someDate is in the format of MM/dd/yyyy
if(someCalendar2.compareTo(someCalendar1) < 0){
...Code... ...
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When testing for equality of strings in Java I have always used equals() because to me this seems to be the most natural method for it. After all, its name already ... |
I'm getting a "java.lang.string cannot be cast to node" exception. I thought of converting the localRoot to a string using a provided toString method then comparing them, nut this leaves no ... |
I'm trying to establish a new sort criteria, in this case by name.
I'm facing an error when I call the sort method...
this is a separated class (SortByName) in package "package":
-----------------------CLASS SortByName---------------------------
package ... |
The Java documentation for Comparable recommends that compareTo be consistent with equals (because of the behavior in sorted sets or sorted maps).
I have a Player object which is mutable. ... |
I don't see anything that I am doing wrong, but NetBeans gives me the following error:
incomparable types
required: boolean
found: java.lang.Object
public int compareTo(Object obj) {
if( obj instaceof Employee){
...
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I've got a question about SimpleDateFormat class and the java.util.Date's compareto method:
I'm constructing a Date object, then I format, finally I parse the formatted string and compare to the original date. ... |
I believe this question applies equally well to C# as to Java, because both require that {c,C}ompareTo be consistent with {e,E}quals:
Suppose I want my equals() method to be the same as ... |
Here is my code:
> import java.util.Scanner;
import java.util.Arrays;
/**
This class tests the Person class.
*/
public class PersonDemo
{
public ...
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I am clueless here...
1: private static class ForeignKeyConstraint implements Comparable<ForeignKeyConstraint> {
2: String tableName;
3: String fkFieldName;
4:
5: public int compareTo(ForeignKeyConstraint o) {
6: if ...
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When implementing compareTo(), does the degree of "difference" need to be taken into account?
For instance, if I have 3 objects, C1, C2, and C3, such that C1 < C2 < C3. ... |
I am having trouble understanding how to use the indexOf() and substring() and compareTo() methods to flip people's first name with their last name in an array.
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in "A Programmers Guide to Java SCJP Certification" I found an example which I can't follow.
This the given enum:
enum Scale3 {
GOOD(Grade.C), BETTER(Grade.B), BEST(Grade.A);
...
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I need a sorted set of objects and am currently using the TreeSet. My problem is that the compareTo of the objects will often return 0, meaning the order of those ... |
I want to sort objects based on Boolean values and I want to sort true values before false values.
Which of these implementations of compareTo is more readable?
Using -1 to change default ... |
Hello
I want to compare two object based on 5-tuple which are:
srcAddr, dstAddr, srcPort, dstPort, protocol
here is what i have:
public class Flows implements Serializable, Comparable {
String srcAddr, dstAddr, srcPort, dstPort, protocol;
public int ...
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here is my compareTo method, but im still getting "missing return statement" warning.
can anyone tell me what is wrong with my code?
public int compareTo(Flows other) {
...
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if I need to customize my code with this logic
if this.srcAddr=other.srcAddr or
this.src.Addr = other.sdstAddr
this.srcPort=other.srcPort
this.srcPort=other.dstPort
because I am going to consider bi-directional flow, a packet from source to destination and a packet from ... |
Actually i'm comparing two string which returns true when i use equals method. Whereas when i use compareTo method it returns 22.
Also i want to know at what place those ... |
Inside of Java's ByteBuffer is the method compareTo for implementing Comparable<ByteBuffer>...
public int compareTo(ByteBuffer that) {
int n = this.position() + Math.min(this.remaining(), that.remaining());
for ...
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public class BigFraction
{
private BigInteger num;
private BigInteger denom;
//public static final BigFraction ZERO;
/**
*
* Creates a BigFraction with numeriator BigInteger.ZERO and denominator BigInteger.ONE
*
...
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I can use it to sort by emp id but I'm not sure if it is possible to compare strings. I get an error the operator is undefined for strings.
public int ...
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What is the difference between return 0, return 1 and return -1 in compareTo() in java?..
Regards,
magggi
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I'm having a strange problem comparing strings. I send a string to my server (as bytes using getBytes()) from the client. I've ensured that encoding is the same on the client ... |
I'm debugging erroneous search returns from my data structures class project. This current project required us to build an ordered unrolled linked list, and run a search on the contents, ... |
Ok I am trying to finish this program for my into to java class and I am having trouble with this one part. Everything else is working except this. I have ... |
I am trying to write a program for my course that sorts an array of objects.
Does anyone know why I am getting this error? Snippets of code included below!
Student object
/* Class ...
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I want to sort a list List<Blabla> donnees by a criterion on one of its field. My problem is that compareTo is already overriden for this Class. So I've got something ... |
I just found this statement: "One can greatly increase the performance of compareTo by comparing first on items which are most likely to differ". Is it true? And if it is, ... |
I have an assignment where I need to create an arraylist of BookInventory objects with params (String bookNum, String bookTitle, int qoh, double bookPrice). Where bookNum is the hyphenated ISBN ... |
I'm trying to implement a heap using a PriorityQueue as follows:
PriorityQueue<Node> heap = new PriorityQueue<Node>();
Set<String> allWords = codebook.getAllWords();
for(String word : allWords)
{
heap.add(new Node(word, codebook.getProbability(word)));
System.out.println(heap.toString());
}
Where ... |
How do i go about using compareto for a double and i want to turn it into an int?
An example would be nice. I have been searching the java api.
also is ... |
I want to compare two strings with the method string.compareTo(anOtherString); and it delivers me a strange value... (i need an integer value between 0 and 57 for every string)
In the following ... |
I am trying to read in a vector of companies and returns true if two companies have the same name, false otherwise Which I have done using ComapareTo method. In my ... |
According to the JavaDoc for BigDecimal, the compareTo function does not account for the scale during comparison.
Now I have a test case that looks something like this:
BigDecimal result = ...
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I have this method in my code
public boolean has(AnyType x){
for(int i=0; i<items.length; i++)
...
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I'm using Collections.sort() to sort a list of MP3s in order of runtime, and if runtime is equal, then sort alphabetically by title, and if title is equal then sort by ... |
I'm using Collections.sort to sort a ArrayList of objects, and I want to see if there is a more efficient compareTo method for what I'm trying to do.
Here's the method:
@Override
public int ...
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It is said that when input parameter is null, compareTo() should throw a NullPointerException. However, I am implementing a class which needs to compare fields with the type of String. These ... |
I have a question about making a compareTo function in Java.
In Java, we have the String.compareTo(String) method.
However, I need to make a compareTo function with only only parameter, like: compareTo(String).
I assume ... |
i'm a little confused with all the "If the ordering imposed by c on S is inconsistent with equals, the sorted set (or sorted map) will behave strangely." warnings in the ... |
I have this class:
public class Sample implements Comparable<Sample> {
public String a;
public String b;
public String c;
public int compareTo (Sample sampleToCompare) {
int compResult = this.a.compareTo(sampleToCompare.a);
return (compResult != ...
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Consider the simple test class:
import java.math.BigDecimal;
/**
* @author The Elite Gentleman
*
*/
public class Main {
/**
* @param args
...
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Strangely, instance variable brand is private scope, yet accessible the "public" way inside of method compareTo.
public class Car implements Comparable<Car> {
private String brand;
public ...
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I'm looking for best practice for the definition of the compareTo() method in the case where the class implements Comparable. Thus, the signature of the method has to be
public int ...
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I have a class implementing a data structure storing Comparable objects.
Some instances hold Longs and other Strings.
I want to count the number of comparisons that occur, without changing the data structure ... |
The following little test throws an NPE:
public class Test {
public static void main(String[] args) {
String a = "a";
...
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I am implementing Comparable interface on a trivial class that wraps a single int member.
I can implement it this way:
@Override
public int compareTo ( ...
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I'm trying to pull my app version from my DB which is 1.2.0 and compare it to the installed apps current version. which may be undefined or lower (e.g. 1.1.0 etc..).
I ... |
I'm trying to write a simple procedure that will add to a List every second Monday (every pay period day) since the beginning of the year, what is happening is kind ... |
I have a code snippet which I am not able to understand what exactly it does..
This code is in JavaBean..
private Object myNumb;
//then getter and setter for this
public int compareTo(myRptObj o){
...
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Possible Duplicate:
Java Strings: compareTo() vs. equals()
In java, I am reading an excel file. The value in a particular cell is fetched into a string, ... |
I was wondering if the compareTo method looks at just the length of the strings or if it looks at each character of the string?
and if it does just look at ... |
I know this has been an issue for a while now, and checked all previously answers I could get, but still this one doesn't work.
The object 'crew' represents crewmembers with ranks ... |
I'm new to using the comparable interface, so hopefully this has a simple fix... I've created a class Fraction used to store fractions and it implements the comparable interface. I overrided the compareTo method. With this code... public int compareTo(Object otherFraction) { double f1; double f2; int num; String temp; //check for valid object to compare to if (!(otherFraction instanceof Fraction)) ... |
I have an object that has an index field and overrides the compareTo method. I can sort lists of these objects by that field. When a list of these objects are sorted - how is the compareTo method called? Does every object simply compare itself to the next object in the list? Depending on the answer to the above questions. Would ... |
Hi All I am using Collections.sort(ArrayList containg objects) I want to sort the object by Date field. So i have overridden compareTo method but since many dates are null so it is giving NUll pointer exception. I have checked null only for instance variable like if(li_myDate!=null) li_myDate.compareTo(obj.getmyDate()) but since some obj.getMyDate are null , it is giving null pointer exception. What ... |
I have 3 BigDecimal variables: a, b and c. I then do the following test: if( a.add(b).compareTo(c) == 0 ) a = 49.9900000000000001827363995 b = 50.01 c = 100 This sum does not equal zero. How do I set the scale/rounding for all three BigDecimals to get the desired result to equal zero? These are dollar and cents amounts. Thanks, Joe ... |
Hi, I have a table that I'm trying to sort using a CompareTo. The problem is that the table I'm sorting has strings, ints, and dates so when I click the integer column, it "sorts", but not correctly. As you can see, the code below works with Strings. I need to adapt it, if possible, to work with ints and Dates. ... |
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Hi, As per the contract of compareTo method, it is a "natural comparison method". This means that this method should be used only to compare objects for order, and not to check equality of two objects. Then, why do Set use compareTo method, instead of equals method, to eliminate duplicate items. It expects compareTo() to be consistent with equals. Isn't a ... |
Calendar cal = Calendar.getInstance(); java.util.Date todaysDate = null; java.util.Date endDate = null; SimpleDateFormat SDF = new SimpleDateFormat("MM/dd/yyyy hh:mm:ss aaa"); try { todaysDate = cal.getTime(); endDate = SDF.parse("10/16/2006 01:42:27 PM"); int result = endDate.compareTo(todaysDate); System.out.println(" This is the result " + result); } catch (ParseException pe) { //Ignore } output on windows box: This is the result -1 output in linux environment: ... |
Your code should not work, also not on 1.4, if the API documentation says that the object must be a Timestamp object. If it does work on Java 1.4, then that's a bug in Java 1.4. If your program relies on this bug, then you should correct your program, because you don't want your program to rely on a bug in ... |
Hi, I have this view object, public class ReceitaEstadoVO implements Comparable{ private final Date data; private final String regiao; private final double valor; public String toString(){ StringBuffer sb = new StringBuffer("["); if(regiao != null) sb.append("regiao=" + regiao + ";"); if(data != null) sb.append("data=" + data.toString() + ";"); sb.append("valor=" + valor + "]"); return sb.toString(); } public boolean equals(Object obj){ boolean result ... |
We are upgrading to jdk 1.5. I am getting compilation errors due to compareTo method which were working in jdk 1.4 Here is what I get method compareTo(Integer) in the type Integer is not applicable to compareTo(Object). I know I can simply cast the object to Integer but is it possible without casting or is it a change that came wioth ... |
I was working with the compareDates method to compare 2 dates for some reason my code returns the getTime() with a difference The code does not works fine when the dates are same I have a date object from the database and the second one is created this way Calendar cal = Calendar.getInstance(); cal.set(2008, 8, 01,0,0,0); Date dateConstant = cal.getTime(); I ... |
Hi, In the below code when i sort the array , they are passing to entries of map and comparator, then why do we have compare and compareTo both , what is called for comparing ? Arrays.sort(entries, new Comparator() { public int compareTo(Object lhs, Object rhs) { Map.Entry le = (Map.Entry)lhs; Map.Entry re = (Map.Entry)rhs; return ((Comparable)le.getValue()).compareTo((Comparable)re.getValue()); } public int compare(Object ... |
HI, This is a program that compiles but doesn't run. I get the error that the constructor rectangle[i]= new CompareRectangle is a malformed expression. Could someone help with this? THANKS!!! Mary Ellen CompareRectangle.java--This program will create a class named CompareRectangle that will extend Rectangle and implement CompareObject. Implementation of the compareTo() method that will compare the rectangles on their areas will ... |
I've got an odd little problem: two strings which appear to the naked eye to be identical are showing up as different when I use java.lang.String.compareTo(String). The relevant code is: ... byte good[] = welcome.getData(); String goodStr = new String(good); String want = new String("GDNP OK\n\n"); System.out.println(want); int wasGood = goodStr.compareTo(want); System.out.println(wasGood); if (wasGood == 0) { didOK = true; System.out.println("Got ... |
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My question is fairly simple but I am unsure of the answer. If I have a class that has a compareTo method written in it, then derive another class from that and write a compareTo method in it, is the child class overriding the compareTo method of the parent class or of the Object class? Regards, Michael |
Hey yall, Iam having a problem putting this together. This is all the information that I have. I will post the code below. But I am to check if the disks in my Disks are in ascending order, using the compareTo method in the class Disk. Im not to sure about the setMyDisks method as well. I would appreciate any input ... |
Hi! Can anyone tell me whats wrong here? Pls, any help is appreciated. Here is my code: import java.util.*; class Testa implements Comparable { public static void main (String argv [] ) { String one="one"; String two="two"; int number=compareTo(); } public static int compareTo() { int resultat=one.compareTo(two); return resultat; } } --------------------------------------------- Here is the compiler errors: G:\Documents and Settings\Santhan\My Documents\Java\Testa.java:4: ... |
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The term lexicographically can be thought of as "alphabetically". That is, "apple" comes before "bug" and so on. Also, shorter words come before longer words. "apple" comes before "apples" This is also dictionary order. The only difference is that on a computer we also deal with special characters like !@#$%^&* that normally don't occur in dictionaries. There are three results from ... |
Hi. I'm hoping somone can help me. I have to put a compareTo() method in my program and I have one written but ehrn I test it my output message gives me an error message Stack Overflow for CompareTo method. Here is what my code looks like. I know it isn't write i'm actually surprised that I got it to compile. ... |
I have a compareTo() method now (with the help of someone from this forum). It's inside a Threat class but needs to be overidden in one of it's subclasses. It needs to be overidden in the Malware class. If both objects are malware it should compare severity (integer), then if that matches it should compare name. Here's the entire program, can ... |
Hi there! I am trying to find out what would be correct syntex for declaring a compareTo() method and invoking it from the main program. I went through books but I didn't find anything related to compare two integers (but I found for String comparison). I also found suggestion for using interface but I'm not sure how to implement that. Can ... |
Hi, I have a little problem with the compareTo method. I want to compare two strings, and if they are not equal to each other, I want it to recurse with a new input from the user. I'm not sure about how to say if 'two strings are not equal to each other'. Do I use !=0 or <>0. Here is ... |
Well, I can point out three things here; two of them are going to make the code work incorrectly, one is an efficiency thing. 1) The Java idiom for a "for" loop over a list is: for (int counter=0; counter < list.size(); ++counter) If the list is 10 items long, counter will take the ten values from 0 to 9; it ... |
Only since Java 5.0. It is true that equals always needs Object as its type. I guess it's so you can check if an object is equal to any other object. It's like asking: is this apple the same as that orange? The answer is false obviously, but it's still a valid question. For Comparable in Java 1.4 and before you ... |
For compareTo() go to the API documentation for the Comparable interface, and it tells you what you have to implement. For sorting, many methods use a version of recursive merge sort with omission of already-sorted subsets. Merge sort has the advantage of being stable (it doesn't swap round two objects with the same value) whereas the faster quicksort might swap them ... |
Hello friends its Vibhas can anybody explain me my doubts in this following code and also please cheak my comments wheather my understanding is correct or not... My doubt part is marked as //??? part which is the last line please clarify it here is the code import java.util.*; public class Dvdinfo implements Comparable { String title; String genre; String leadActor; ... |
Ladies/Gents, OK, so, generics are becoming slowly clearer to me, but still having a few troubles. I implemented a function, min(), which should return the smallest element in an array. I think my function will work, but can't be sure, because now I can't compile. The specific error I'm getting is that I'm not overriding compareTo() in this class. Now, I ... |
Hello, This is my first post, so I hope I am doing this correctly. I am studying Programming at University (College) and am a little stuck on the CompareTo method in the Comparable interface. What I need to do is: If the price is equal (return 0), then compare the area's. I hope this is clear enough, here is my code: ... |
Hello, There is a function to read a file and list in a table, the file has values as below: #id, userName, emailAddress 1 = 1, name1, emailA 2 = 2, nameC, emailYY .... 13 = 13, name13, emailKK when the table is ordered by id, the String.compartTo(String) method is used, and the result is like: 1, 10, 11, 12, 13, ... |
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What is not clear? What do you understand? Do you really expect someone to write an entire essay on the topic, when there are scores of them already out there? And since you didn't understand those, why would you understand one written here, without telling us what EXACTLY you need clarification on? Your job, when you post a question here, it ... |
equals() checks if two objects are the same or not and returns a boolean. compareTo() (from interface Comparable) returns an integer. It checks which of the two objects is "less than", "equal to" or "greater than" the other. Not all objects can be logically ordered, so a compareTo() method doesn't always make sense. Note that equals() doesn't define the ordering between ... |
public class Sringimp { static String arr[] = {"xem","zap","are","rat","sat"}; public static void main(String args[]) { for(int j = 0;j |