- Can constructor have return type?
- Are Ndarrays mutable?
- Is kotlin ArrayList mutable?
- Are arrays mutable asList?
- Is HashMap immutable?
- Are strings mutable in Java?
- Are arrays in Java mutable?
- Can we override key in HashMap?
- What happens if we put a key object in a HashMap which exists?
- Can we declare list as final?
- Can we declare array as static?
- Can we declare ArrayList as final?
- What is mutable vs immutable?
- Can we put object as key in HashMap?
- Is ArrayList immutable in Java?
Can constructor have return type?
No, constructor does not have any return type in Java.
It does not have a return type and its name is same as the class name.
Mostly it is used to instantiate the instance variables of a class.
If the programmer doesn’t write a constructor the compiler writes a constructors on his behalf..
Are Ndarrays mutable?
Numpy Arrays are mutable, which means that you can change the value of an element in the array after an array has been initialized. … Unlike Python lists, the contents of a Numpy array are homogenous. So if you try to assign a string value to an element in an array, whose data type is int, you will get an error.
Is kotlin ArrayList mutable?
Now we can see that listOf() returns a Java mutable list ( java. util. Arrays$ArrayList) under the Kotlin non-modifiable List interface ( kotlin. collections.
Are arrays mutable asList?
Arrays. asList() , the list is mutable. … That means that it is not possible to add elements to the list or remove elements from the list. The reason simply is that the list is still backed by the array, and the size of the array may not change.
Is HashMap immutable?
String, Integer and other wrapper classes are natural candidates of HashMap key, and String is most frequently used key as well because String is immutable and final,and overrides equals and hashcode() method. … Both hashcode and equals method are used in put and get method of HashMap.
Are strings mutable in Java?
In java, string objects are immutable. Immutable simply means unmodifiable or unchangeable. Once string object is created its data or state can’t be changed but a new string object is created.
Are arrays in Java mutable?
An immutable data type can’t be changed once it’s created. The more restriction(like immutability) you have on a class, the better. For example, In Java, String, Integer, Double are Immutable classes, while StringBuilder, Stack, and Java array are Mutable.
Can we override key in HashMap?
If you want to make a mutable object as key in hashmap, then you have to make sure that state change for key object does not change the hash code of object. This can be done by overriding the hashCode() method. But, you must make sure you are honoring the contract with equals() also.
What happens if we put a key object in a HashMap which exists?
What happens if we put a key object in a HashMap which exists? Explanation: HashMap always contains unique keys. If same key is inserted again, the new object replaces the previous object. 5.
Can we declare list as final?
You can still change, add and remove the contents of the list, but cannot create a new list assigned to the variable. … A variable can be declared final. A final variable may only be assigned to once.
Can we declare array as static?
Statically declared arrays are allocated memory at compile time and their size is fixed, i.e., cannot be changed later. They can be initialized in a manner similar to Java. For example two int arrays are declared, one initialized, one not. Static multi-dimensional arrays are declared with multiple dimensions.
Can we declare ArrayList as final?
final ArrayList list = new ArrayList(); this means that the variable list will always point to the same ArrayList object. … When using inner classes you need to declare variables as final in an enclosing scope so that you can access them in the inner class.
What is mutable vs immutable?
A mutable object can be changed after it’s created, and an immutable object can’t. That said, if you’re defining your own class, you can make its objects immutable by making all fields final and private. Strings can be mutable or immutable depending on the language.
Can we put object as key in HashMap?
Answer to your question is yes, objects of custom classes can be used as a key in a HashMap. … If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
Is ArrayList immutable in Java?
If you create a List and pass it to the Collections. unmodifiableList method, then you get an unmodifiable view. The underlying list is still modifiable, and modifications to it are visible through the List that is returned, so it is not actually immutable.