why use null != anything instead of anything!=null? [duplicate]
anything != null is exactly equivalent to null != anything. On the other hand, "true".equals(x) avoids the need to check if x is null when doing x.equals("true")....
How to show !equals in if statement (Java)? [duplicate]
java,if-statement,for-loop,equals
You can use the NOT operator ! with appropriate parentheses for clarity (though not strictly required). if (!(condition)) so in your case.... if(!(doglist.get(g).equals(name))) ...
Should I override the Object.equals(Object) method?
java,equals,equality,object-comparison
Yes, you have to override it. By not doing that, you are using the version that Object itself provides, which defaults to reference equality (they are the same "physical" object). Depending on your IDE, this could be written automatically for you. For instance, IntelliJ 14 just wrote this for me:...
GLSL component-wise equal comparison
opengl,vector,comparison,glsl,equals
bvec is the return type of the equal function. You get a vector of booleans to tell you which components are equal. If you just want to compare the entire color, then use the equality operator ==.
comparing two dates. Equal isn't working as well
sql,date,ms-access,compare,equals
The Date/Time value #2015.06.11# includes a time component, which is 12:00 AM. If any of your stored values for that date include a time component other than 12:00 AM, they will be excluded by your WHERE clause. Use a modified WHERE clause to retrieve all the rows for your target...
Java how does HashMap identify the key object if hashCode are the same and equals is true?
Your implementation of equals() is violating the contract (it is not symmetric), that's why it does not work correctly. You need to use something like: @Override public boolean equals(Object obj) { if (obj instanceof TypePair) { TypePair objTypePair = (TypePair) obj; return a .isAssignableFrom(objTypePair.a) && b .isAssignableFrom(objTypePair.b) || objTypePair.a.isAssignableFrom(a) &&...
Overriding equals and hashCode on a POJO with a List object
Short version: Yes, you can use the append method of EqualsBuilder and HashCodeBuilder. Long version: The List.equals(Object) method compares all the elements on the list. See the javadoc Compares the specified object with this list for equality. Returns true if and only if the specified object is also a list,...
when to implement comparable and when to implement equals in Java
java,equals,hashcode,comparable
If you only ever need to compare them for equality (or put them in a HashMap or HashSet which is effectively the same) you only need to implement equals and hashcode. If your objects have an implicit order and you indend to sort them (or put them in a TreeMap...
Check objects equality without equals overriding in java [closed]
You could use EqualsBuilder.reflectionEquals(this, obj); in Apache Commons EqualsBuilder
Why is the input parameter of Equals of type Object?
Your assumptions are wrong: Equality operation is semantically speaking checking if two thingies are a copy of itself. Generally, it's done based on the pointer (reference value or whatever one might want to call it). That's Reference equality and it's checked by the function Object.ReferenceEquals (which is static and not...
Item-9: “Always override hashCode() when you override equals”
It would be impossible for hashCode() to always return different values for unequal objects. For example, there are 2^64 different Long values, but only 2^32 possible int values. Therefore the hashCode() method for Long has to have some repeats. In situations like this you have to try hard to ensure...
Java - method equals and more possible letters
For identifying characters you can use the following (Java Character): Character.isLetter(<target_char>) And if replacement is to be done, following would help you replace characters from a-z: <target_string>.replaceAll("[a-zA-Z]",<replacement>) ...
Equals Method in Enum Type
Enums are compared as Objects. These are two distinct objects of different classes. Why should they be equal? A,B,C - are just names of variables. They mean nothing in comparison operation.
Overriding .equals() method (== returned true while comparing Strings)!
java,caching,equals,referenceequals
This is because of string interning. The string literals "Jon" and "Smith" are compiled into the same string and saved in the string constant pool by the compiler. Hence in this case, both constructors would reference the same instance. You can see the difference using the below: Employee e1 =...
Floated Sidebar: How to get sidebar full height of window?
css,height,equals,viewport,sidebar
Giving position:absolute; and 100% height to the sidebar will do. http://jsfiddle.net/07zLb3xx/ #sidebar { height: 100%; position: absolute; right: 0; } If you have problems with the sidebar going out of the parent wrapper, give position:relative; to the parent wrapper like this http://jsfiddle.net/07zLb3xx/1/...
Can/should one write a Comparator consistent with Object's equals method
This is described in the documentation of Comparator: The ordering imposed by a comparator c on a set of elements S is said to be consistent with equals if and only if c.compare(e1, e2)==0 has the same boolean value as e1.equals(e2) for every e1 and e2 in S. Caution should...
Why are this == other and and this.hashcode == other.hashcode() giving different results?
A hash code, by definition, contains less information than the source data. This means that collisions are possible, and in that case you will have two objects with same hash code but which are not equal. The general requirement of Java hashCode() are in the opposite direction: two objects for...
calling super.equals() in derived class while overriding equals
java,inheritance,equals,overriding
So the equals() method is implemented correctly and it works in the following way: delegate the comparison of the age and name to the Base class if it is not the same, return false otherwise compare the value of the bonus field in the Derived class The call of super.equals()...
Cannot resolve method equals(java.lang.Long)
Why does it seem like it doesn't return a Long object? 15.18.2. Additive Operators (+ and -) for Numeric Types tells us that: Binary numeric promotion is performed on the operands. The type of an additive expression on numeric operands is the promoted type of its operands. And 5.6.2....
how to combine the elements of a list representing the elements of a Bash command to a new list featuring the equals symbol
python,list,command,arguments,equals
You could use re module here. >>> commandOptionsAndArguments = ['myBigTool', '--num-callers', '30', '--leak-check', 'full', '--tool', 'memcheck', '--suppressions', 'etc/valgrind-root.supp', '--suppressions', 'Gaudi.supp/Gaudi.supp', '--suppressions', 'oracleDB.supp', '--suppressions', 'valgrindRTT.supp', '--suppressions', 'root.supp/root.supp', '--mySpecialFlag', '$(which python)', '$(which athena.py)', 'athenaConf.pkl'] >>> re.split(r'\s+(?![^()]*\))', re.sub(r'(--\S+)\s+(\w\S+)', r'\1=\2', '...
Issue with .equals()
Whenever a comparison doesn't return what you think it should, check that the types are what you think they are. String#split returns an array of Strings. For your given input the first element of that array will be "1". If lineNumber is something other than a String, say an int,...
How can I get the return value of a superclass method without executing it?
You cannot run the method without letting it print anything. This is why most of your methods should not have "side effects" (like printing things to the screen). Remove the println calls from both equals methods. Add them to the code that calls equals instead....
How to check a spinner which contains a string is not equal to another string?
android,equals,android-spinner
To get the selected string from a spinner and check if it's equal to another one: String selectedString = (String)spinner.getSelectedItem(); if(selectedString.compareTo(anotherString) != 0) { // Stuff to do when strings are not equal. } ...
Java equals causes ArrayIndexOutOfBoundsException
java,equals,indexoutofboundsexception
Your exception is on this line - String s1 = tmp.opisTovora[0]. It means that tmp.opisTovora is an empty array, so tmp.opisTovora[0] is out of the bounds of that array. It has nothing to do with equals....
custom equals() method does not work properly
java,map,override,equals,hashset
You should always override hashCode when you override equals and vice versa. Add something like this to your Rule class: @Override public int hashCode() { return left.hashCode() ^ right.hashCode() ^ lookupArtist.hashCode(); } Here is a good answer explaining why it's important to override both. Also, your equals method can be...
Implementing hashCode for a BST
java,binary-search-tree,equals
I cannot just add the values of the node to check if the trees are equal. Sure you can. hashCodes do not have to be unique, and if two BSTs have the same contents, then summing the node contents will give you the same results in each case, which...
Hangman game; why doesn't .equals work? [closed]
You are comparing guess, which is a String to a single character in result. In order for equals to work, you need to compare objects of the same type, e.g.: if (guess.equals(String.valueOf(result.charAt(i)))) { ...
Java equals() and hashCode() changes
One problem is that you won't be able to find that object in a HashSet or a HashMap (when that object is a key in the Map) if its hashCode changes after to add it to the Collection. Changing the result of equals during the lifetime of an object may...
EqualsIgnoreCase function - Exception : org.apache.pig.backend.executionengine.ExecException
Yes you are right, string functions EqualsIgnoreCase and TRIM are not able to handle blank string in the input. To solve this issue,what ever you did in the last stmt is right, just remove the Trim function it will work. C = FILTER A BY (value is not null) and...
string less or equal datetime django
try with strptime of time time module check_date = time.strptime('2014-12-29 23:59:59', "%Y-%m-%d %H:%M:%S") Attendance.objects.filter(start_date__lte=check_date) ...
Checking if pairs are equal
otherObject is declared as just an Object type, so it doesn't have any of the attributes of whatever class you created. It should be the same type as the object you are trying to compare it with.
Javascript not greater than 0 [closed]
javascript,jquery,if-statement,equals
You need a second set of brackets: if(!(a>0)){} Or, better yet "not greater than" is the same as saying "less than or equal to": if(a<=0){} ...
R - Get row numbers where two matrices have equal rows
Alternatively you could use match_df from plyr: match_df(data.frame(A),data.frame(B)) Matching on: X1, X2, X3 X1 X2 X3 2 4 5 6 3 7 8 9 And to extract the numbers of the rows you could type as.numeric(rownames(match_df(data.frame(A),data.frame(B))))...
Equals method for PlayingCard Class, how to get working?
This is not doing quite what you may think: if (getClass() != otherObject.getClass()) You are comparing Class object references here. Even if the Classes are of the same type, they may have different Class object references returned by their respective getClass() methods. Better yet, use the instanceof operator. @Override public...
Why do I get a wrong output of equals method?
else if (this.getP1() == S.getP1() && this.getP2() == S.getP2()) return true; else if(this.getP1() != S.getP1() && this.getP2() != S.getP2()) return true; These tests basically returns true if both points of the two segments are equal or they are both different to each respective other. This is redundant and wrong since...
Graphviz how to separate nodes equally (possibly with nodesep)?
position,equals,distance,graphviz
This may be a case for invisible nodes (and edges...). Just add some invisible nodes between the rank=same subgraph to force exactly one node between the lines: graph Example { rankdir=LR ordering=out { rank=same b1 [group=b] c1 [group=c] d1 [group=d] e1 [group=e] // invisible nodes node[style=invis] edge[style=invis] b1--i1--c1--i2--d1--i3--e1 } node...
Costs of binary operations
At least for basic types, it wouldn't be any more costly. Essentially they would all call the same compare function, say C(a, b), and process the return -1, 0 or +1. For example >= would translate into C(a, b) != -1, == as !C(a, b), etc. In some languages though,...
Hashing Equals only returns true
collections,map,hashmap,equals,hashcode
I'm guessing you're surprised that not all of them are Employee 5? Equals always returns true so e5 should have overwritten all of them, right? A HashMap uses "buckets" behind the scenes. Let's say that there's only 2, to make it simple. A real HashMap has a lot more. When...
Is it possible to generate equals and compareTo methods for classes generated with jaxb
Ok, here's another approach. You could use the -XcodeInjector plugin to add hashCode and equals methods. See this question: Inserting code with XJC+xsd+jxb using the options " -Xinject-code -extension " Something like: <jxb:bindings schemaLocation="schema.xsd"> <jxb:bindings node="/xs:schema/xs:complexType[@name='MyItemType']"> <ci:code> @Override public int hashCode() { return guid == null? 0 : guid.hashCode();} </ci:code>...
setting objects equal to eachother (java)
java,methods,compiler-errors,equals
There are two ways to interpret "set the objects equal to each other". One is that you want p1 and p3 to refer to the same object. Like how Clark Kent and Superman are two names (references) for the same person. This would be accomplished by: Person p1 = new...
How to override hashcode and equals method to avoid adding duplicate strings in HashSet in java?
java,equals,hashcode,hashset,java-collections-api
Try this @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + ((placeId == null) ? 0 : placeId.hashCode()); return result; } @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false;...
Why assertEquals and assertSame in junit return the same result for two instances same class?
Since you didn't override equals in your class, assertEquals behaves the same as assertSame since the default equals implementation compare references. 150 public boolean equals(Object obj) { 151 return (this == obj); 152 } If you provide a dumb overriding of equals: class SomeClass { @Override public boolean equals(Object o)...
Assigning fields in an equals() method
java,equals,lazy-initialization
The approach you describe is sometimes a good one, especially in situations where it is likely that many large immutable objects, despite being independently constructed, will end up being identical. Because it is much faster to compare equal references than to compare large objects which happen to be equal, it...
How to compare two Strings when both can be null? [duplicate]
If Java 7+, use Objects.equals(); its documentation explicitly specifies that: [...] if both arguments are null, true is returned and if exactly one argument is null, false is returned. Otherwise, equality is determined by using the equals method of the first argument. which is what you want. If you don't,...
Is there any difference between == null and .equals(“null”)?
validFolderRow.getBondTAFolderType() == null compares to null (i.e. checks if validFolderRow.getBondTAFolderType() is null). validFolderRow.getBondTAFolderType().equals("null") compares validFolderRow.getBondTAFolderType() to a String whose value is "null". Note that first comparison must be done first, since if validFolderRow.getBondTAFolderType() is null, you can't call equals on it (since it will throw a NullPointerException). Since || is...
Annotating a Java class as safe for reference comparison
java,intellij-idea,equals,equality,multiton
The IntelliJ inspection has an option "Ignore '==' between objects of a type with only private constructors". If I understand correctly, enabling this option will turn off the highlighting in your case. There is currently no possibility in IntelliJ IDEA to ignore the == comparison based on an annotation....
Should I check collections when overriding equals in entities?
Whether or not you check the equality of all the member entities is a question of your definition of equality. Note that you cannot correctly override equals() at all without overriding hashCode() as well to ensure that equal objects have equal hash codes. With that said, opinions vary on whether...
Java HashMap return value not confirming with my understanding of equals and hashcode
Actually, you got it backwards. The value was overridden. The key wasn't replaced since as far as HashMap is concerned, e and e2 are identical. Your output is {1--e=e2, 2--e1=e1}: key = e, value = "e2" (which overrode the old value "e") key = e1, value = "e1" ...
PHP echo only if string match [duplicate]
php,json,if-statement,echo,equals
You used assign (=) instead of is equal (==) It should go like this: if ($sub == 'YES!') { echo $sub . '|'. 'http://site/level/' . $no . '<br />'; } ...
Maintaining hashCode contract for the specific condition, equals() depending on two integers
You're running into trouble because your notion of equality is inconsistent. Specifically, it's not transitive, which the contract for .equals() requires. It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true. Under your definition, e1...
Java questions on equals and compareTo method
java,linked-list,equals,compareto
Your find always returns false because you initialize node and current to null, so the loop is never entered. In addition, you should compare e to the item, not to the Node. It should probably be: public boolean find(E e){ Node current = head; while (current != null){ if (current.item.equals(e)){...
C#, Which class fields/members should be considered when overriding GetHashCode and Equals?
c#,equals,gethashcode,iequatable
The first Equals override method commented is required? Some comparisons use the generic version, some use the non-generic version. Since it's a fairly trivial implementation if you already have the generic version there's no harm in implementing it. In this case, which class members should I include in the...
These if statements and for loops don't work [closed]
You got your logic backwards : for (int j = 0; j < p; j++){ if (!data.get(j).equals(tempTable)){ data.add(tempTable); break; } } This will add tempTable if any of the elements in data is not equal to tempTable. You want to add it only if all the elements are not equal...
Java ArrayList indexOf returns -1
If you check the ArrayList.indexOf implementation, you will see that Vector3i.equals is called in your case. Actually it's even specified in JavaDoc for List: More formally, returns the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index. In general equals operation...
How can I check if an ArrayList contains an Object with a specific field value?
java,arraylist,override,equals,contains
The most elegant solution is to First and foremost fix your equals method so that it fulfills equals contract --- meaning if a.equals(b) then b.equals(a) must be true. You should never have a TeamMember object be equal to a String. That will result in the possibility of hard to debug...
Comparing wrapper class with primitive using equals() gives strange behavior
longWrapper.equals(0) returns false, because 0 is autoboxed to Integer, not to Long. Since the two types are different, .equals() returns false. In the meantime, longWrapper == 0 is true, because the longwrapper value is unboxed to 0, and 0 == 0 without considering the actual primitive types....
Is there any negative consequence in having Equals based on GetHashCode?
No, the documentation states very clearly: You should not assume that equal hash codes imply object equality. Also: Two objects that are equal return hash codes that are equal. However, the reverse is not true: equal hash codes do not imply object equality And: Caution: Do not test for equality...
Why doesn't or operator work in if statement when using “not equals”?
De Morgan's Laws for Boolean operations are an important skill for a programmer to understand intimately. In your case, when negating you need additional parentheses to correctly order the operations, or as in your case change the || to an &&. To use the || you'd put if (!(userName ==...
crash on compare Spinner selected item to String
Add check that getSelectedItem() is not null, if you haven't select anything manually it is not set.
Overriding equals method in Scala
email is only a constructor parameter and not a member of the class itself. You can make it as such by preceding it with val class Player(val email: String) { override def equals(player: Any): Boolean = { player match { case p: Player => email.equals(p.email) case _ => false }...
Checking if usernames exists, case-sensitive [duplicate]
c#,string,entity-framework,equals
String.equals() is case sensitive, but EF will translate that into SQL, which may not be case-sensitive depending on the collation of that column (or your database if the column does not have a collation specified). You can solve this on the server side by setting the collation of that column...
Java - remove objects in a collection that are in another collection, with an arbitrary meaning of “equals”
You mention that it's Java 8. In that case you have a very simple and straightforward way to achieve this: list1.removeIf(item1 -> list2.stream().anyMatch(item2 -> customEquals(item1, item2)); If your customEquals method is a member of Item you could use a method reference to make it a bit neater: list1.removeIf(item -> list2.stream().anyMatch(item::customEquals));...
Slow dictionary with custom class key
c#,string,dictionary,equals,gethashcode
As others have said in the comments, the problem is in your GetHashCode() implementation. Taking your code, and running 10,000,000 iterations with the string key took 11-12 seconds. Running with your existing hashCode I stopped it after over a minute. Using the following hashCode implementation took under 5 seconds. public...
Implementing equals and hashcode for a BST
Will the following work iff the trees are equal in both structure and content? root.hashCode() == otherRoot.hashCode() No, it would not work, because hash code equality is a one-way street: when objects are equal, hash codes must be equal. However, when objects are not equal, hash codes may or...
Optimize performance of a equal method to mark multiple rows in a DataGrid
You can use HashSet<ICoreItem> instead of SortedList<ICoreItem, ICoreItem>: private void SelectingCoreItems(SortedList<ICoreItem, ICoreItem> sortedList) { var lookup = new HashSet<ICoreItem>(sortedList.Select(i => i.Key)); for (int i = 0; i < VisibleCoreItems.Count; i++) { CoreItem currentItem = VisibleCoreItems[i]; if (lookup.Contains(currentItem)) { itemListView.SelectedItems.Add(currentItem); } } } Also, it may be slow to compare instances...
Lua - Is it possible to check if 2 functions are equal?
Using == for functions only checks if they reference to the same function, which is not what you expected. This task is rather difficult, if not impossible at all. For really simple cases, here's an idea: function f(x) return x + 1 end local g = function(y) return y +...
How to return a specific item in Distinct using EqualityComparer in C#
c#,list,distinct,equals,iequalitycomparer
Distinct always adds the first element which it see. So it depends on the order of the sequence which you passed in. Source is fairly simple, which can be found here static IEnumerable<TSource> DistinctIterator<TSource>(IEnumerable<TSource> source, IEqualityComparer<TSource> comparer) { Set<TSource> set = new Set<TSource>(comparer); foreach (TSource element in source) if (set.Add(element))...
Comparasion of Integer.equals() and Objects.equals()
Because the JIT kicks in, and detects that Random.nextInt() and equals() are two methods that are often called, and that optimizing them is thus useful. Once the byte-code is optimized and transformed to native code, its execution is faster. Note that what you're measuring is probably more Random.nextInt() than equals()....
MySQL: Sum if rows are equal
If I understand you correctly. You could do something like this: SELECT client, thickness, material, SUM(amount) AS TotalAmount FROM Table1 GROUP BY client, thickness, material ...
Using HashSet with a user class Employee
java,set,equals,hashcode,hashset
You're overloading equals rather than overriding it. Its parameter should be of type Object. But also your hashCode is checking the id while equals is checking the name. They should probably be constructed from the same properties....
Javascript if statement if (ball.style.left === '0px') {
javascript,css,if-statement,equals,semantics
The problem is really simple. I came upon it when I was coding a snake in javascript. When you want to test where the ball is located don't use ball.style.left but ball.offsetLeft. In the demo you'll notice ball.style.left doesn't return anything while the offsetLeft does. Only use ball.style.left when you...
Duplicate values in a hashSet
For your ResultSet class, you defined an equals() method but not a hashCode() method. You need both methods for HashSet to work correctly. Please see this explanation. (It talks about HashMap, but it also applies to HashSet.)
How hashset checks for duplicate elements?
The reason is your hashcode function: (int) (Math.random()%100); always returns 0. So all A elements always have the same hashcode. Therefore all A elements will be in the same bucket in the HashSet so since your equals will always return true. As soon as it finds an A in the...
Checking for equality of RDDs
java,junit,equals,apache-spark
If the expected result is reasonably small, it's best to collect RDD data and compare it locally (just like you've written). When it's necessary to use large enough datasets in tests, there are few other possibilities: Disclaimer: I'm not familiar enough with Spark Java API, so I'll write further sample...
how to subtract ArrayList using removeall() in java?
java,arraylist,override,equals,subtract
Your equals method looks wrong. It makes more sense to compare this.node0 to ((Correction) object).node0. I think it should be: public boolean equals(Object object){ boolean same = false; if (object != null && object instanceof Correction) { same = this.node0.equals(((Correction) object).node0) && this.node1.equals(((Correction) object).node1); } return same; } Also, is...
How does a hashSet admit elements
A Set is composed of buckets to speed up searching. When new object is added to a Set, its hash is evaluated using object's hashCode() method. Then, based on that hash, the Set decides which bucket the object is to be stored in. Then, when you search for an object...
.Net, C# - Boolean.Equal differs from == compare
c#,automapper,equals,boolean-operations
Both results should return true. I have tested your same scenario above and it does return true in both cases. Please see below screenshot. The boolean class overrides the Equals method as follows: public override bool Equals(object obj) { if (!(obj as bool)) { return false; } return this ==...
why is this a good implementation of `hashCode()`
Can someone please explain why is this hashCode good? Why is it unique to a specific object? It's not; essentially no hash code function is. It's just supposed to be rare that two objects have the same hash code, not impossible. What does >> vs. >>> means? I thought...
C# collection with object proxy objects and Equals
c#,list,proxy,equals,nsubstitute
Please check it [TestFixture] public class ObjectEqualsTests { [Test] public void CollectionAddRemoveEntityTest() { const int id = 12345; var list = new List<MyObject>(); var firstObject = Substitute.For<MyObject>(); firstObject.Id.Returns(id); list.Add(firstObject); Assert.IsTrue(list.Contains(firstObject), "Cannot find the first object"); var secondObjectWithSameId = Substitute.For<MyObject>(); secondObjectWithSameId.Id.Returns(id); Assert.IsTrue(list.Contains(secondObjectWithSameId), "Cannot find the second object");...
Duplicate lines in a table as times as value has parameter of a column (in R or in EXEL)
You could also use some wrapper in order to make it easier library(splitstackshape) cbind(bird = 1, expandRows(df, "Sumbird")) # bird Temp OutHum # 1 1 28.7 69 # 1.1 1 28.7 69 # 1.2 1 28.7 69 # 1.3 1 28.7 69 # 2 1 22.3 58 # 2.1 1...
How to make java interface / abstract class that uses per-field equals instead of default equals?
Such feature is provided by Lombok project. It includes annotation processor which is executed during compilation. It's compatible with Eclipse, maven, ant and so on. You should just annotate your class with @EqualsAndHashCode and it will automatically create the equals and hashCode for you.
How to compare two JSON strings when the order of entries keep changing [duplicate]
java,json,string,equals,jsonobject
Jackson Json parser has a nice feature that it can parse a Json String into a Map. You can then query the entries or simply ask on equality: import com.fasterxml.jackson.databind.ObjectMapper; import java.util.*; public class Test { public static void main(String... args) { String input1 = "{\"state\":1,\"cmd\":1}"; String input2 = "{\"cmd\":1,\"state\":1}";...
Java contains() not in accordance with equals()
Actually you should implement Comparable but you should also override the equals. Both are required. Further more, you should make sure that the compareTo method always returns 0 when the equals would return true. If the equals would return false, then also the compareTo should return a value != 0....
Java Compare 2 integers with equals or ==?
int is a primitive. You can use the wrapper Integer like Integer first_int = 1; Integer second_int = 1; if(first_int.equals(second_int)){ // <-- Integer is a wrapper. or you can compare by value (since it is a primitive type) like int first_int = 1; int second_int = 1; if(first_int == second_int){...
Using '==' with strings? (Java) [duplicate]
java,string,equals,equality,sign
== will return true if the objects themselves have the same addresses. For space and efficiency reasons, repeated literals are optimized to use the same address. The second str1 and str2 are equal to the same address, thus == returns true. In the first example, because you are explicitly declaring...
Java - charAt(), equalsIgnoreCase, if statement testing?
java,if-statement,input,equals,charat
equalsIgnoreCase can be used only by Strings. For your case, if you want to use that method, you can do this: Scanner input = new Scanner(System.in); String wesker = input.nextLine(); String letter = wesker.substring(0,1); if(letter.equalsIgnoreCase("y") || letter.equalsIgnoreCase("n")){ System.out.println("Game start"); } else { System.out.println("Game over"); } ...
Java: Map with doubleKey type, how to make the right hashCode()?
java,dictionary,equals,hashcode,multikey
About the only way I can see to do this would be to build a set to TreeSet to cache the hashCodes for the keys. Then use the first equals value encountered as the hashCode value for the current execution. Problems with this: a. Can use a lot of extra...
equals() method not working
First, regarding the compiler error you have, it has nothing to do with the equals() method. It's only because all of the code below, should be inside your main method as it's the only part where you are declaring the variablestwo and four: boolean b = two.equals(four); if (b ==...
Writing an equals() method for linked list object
Your equals method contains an infinite loop. Your while-loop checks to see if n1 != null, but nowhere in the loop do you change the value of n1: while (n1 != null) { if (n1.data != n2.data) { return false; } } You need to advance the nodes down the...
mysql not equal operator not working
I would think that changing and author = any... to and NOT author = any... would work... But if that does not, then I would try doing as a left-join and looking for null. Since the author is the "mid" from the sds_actions, I would write it as... SELECT sp.*...
Understanding equals method
There are typically 2 ways how to check the type in the equals method: Option 1: instanceof if (! (obj instanceof ThisClass)){ return false; } This option respects the Liskov substitution principle. But you cannot add additional properties in sub classes which are relevant for the equals method without breaking...
My equals method output is true while it should be false
if(this.getP1() == S.getP1() && this.getP2() == S.getP2()); ^ Take out this semicolon. Then you will also need to return a value if the if statement isn't met. Edit Currently your if statement is serving no purpose. Take out the semicolon so that the following return statement is qualified by the...