What is the default value for HashMap in Java?

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Java: HashMap: get: specify default value

In Python I can do the following: d = { 'a': True, 'b': False } print d.get('x', True) It will print True In Java, the HashMap.get method does not have the second argument for specifying a default value. What is a correct, terse and readable way of achieving this? The following expression seems too redundant to me: map.containsKey("x") ? map.get("x") : true

Answer:

Both are wrong because they will do 2 lookups. Generally you'll want to do: Boolean ret = map.get("...

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Other solutions

JAVA PROGRAMMERS NEEDED HERE?

Below is my JAVA CODE it is for a vehicle registry application, which records details of different cars. It is capable of storing different records and then displaying what is in the table. The problem is I have tried changing the code so that it stores...

Answer:

You fail on grasping Object. Try to understand the following line, it is like an Array Object nameLabel...

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Did do this java program right?

Can you check if my client class works with my java program? Does my Java Program work with my Client Class? Did I do this Java program right? Java program using clients? Java program encapsulating? How do start this Java Program? Write a class encapsulating...

Answer:

You need to update to the latest version for it to work

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Did I do this Java program right?

Java program using clients? Java program encapsulating? How do start this Java Program? Write a class encapsulating the concept of an investment, assuming that the investment has the following attributes: the name of the investor, the amount of the investment...

Answer:

Yes, I believe you performed the right codings for your Java program! I don't think there are any mistakes...

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Why do we need to declare default constructors in Java classes?

Consider this. Fact: In Java, every variable has a default value. If we don't initialize a variable when it is first created, Java provides a default value to that variable automatically. int has default value as zero. So why would we need to put a default...

Answer:

Compilation Error-Implicit super constructor X() is undefined. Must explicitly invoke another constructor...

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Dhiraj Chandra Drj at Quora Mark as irrelevant Undo

Java Hashmap Question?

For my homework, we are supposed to implement a Contact List(i.e. a phone book) using a hashmap, with the keys being the names of the people and the values being their phone number(s). I have implemented that much correctly. However, we are then supposed...

Answer:

Well, I guess if you cannot leverage the TreeMap to back your contact list then here is one possible...

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yahskara... at Yahoo! Answers Mark as irrelevant Undo

I need help with this java program!! Please!?

Here are the instructions: 1􀀀 Add a private data member bias of type double. This data member will be a number between 0 and 1 that represents the probability the coin will be HEADS when flipped. So, if bias is 0.5, the coin is an ordinary fair...

Answer:

The 2 big mistakes are 1) over-riding the member face in BiasedCoin. 2) not counting heads after you...

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fun_girl... at Yahoo! Answers Mark as irrelevant Undo

Java error in creating multiple new objects?

Write two classes: TestAccount and Account to represent an account. The class contains: a) An int data field named id for the account with value 100. b) A double data field named balance for the account with value 1000. c) A double data field named annualInterestRate...

Answer:

You have not declared the variables you are setting in your constructor. It should be like this : public...

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Java Programming Temperature Application, back to Celsius?

So this is a object of an application Temperatures, which provides the values for the temperature instance. I need a way to convert back to Celsius after the temperatureScale is switch to Fahrenheit of Kelvin. import java.text.DecimalFormat; // Celsius...

Answer:

The hint I can give you is this: this is an understanding question. Let's say you wanted to make a program...

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What does the private hash() function in the HashMap class do?

I was studying the java.util.HashMap source code, and I found the implementation of hash() quite unclear. Could some Java expert explain the rationale behind it?     /**      * Applies a supplemental hash function to a given hashCode, which      * defends...

Answer:

The supplemental hash function simply mixes up the bits of the value returned by the object's hashCode...

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Anand Oza at Quora Mark as irrelevant Undo

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