What does Preconditions checkArgument do?

checkArgument The method checkArgument of the Preconditions class ensures the truthfulness of the parameters passed to the calling method. This method accepts a boolean condition and throws an IllegalArgumentException when the condition is false.

What are preconditions in Java?

Introduction : The Preconditions Class provides a list of static methods for checking that a method or a constructor is invoked with valid parameter values. If a precondition fails, a tailored exception is thrown. When false/null is passed instead, the Preconditions method throws an unchecked exception.

What are preconditions and postconditions in Java?

The precondition is what the method expects in order to do its job properly. A postcondition is a condition that is true after running the method. It is what the method promises to do. Postconditions describe the outcome of running the method, for example what is being returned or the changes to the instance variables.

Do All methods have preconditions?

Sometimes, your methods may not have preconditions. It may be that a client does not need to do or know anything at all to successfully call your method. In those cases, it’s ok to not mention preconditions at all. However, every method should have a postcondition.

What != Means in Java?

Not Equal (!=) The != operator is a comparison operator, also used in conditional expressions. It reads, “not equal”. If the compared values are not equal to each other than the expression returns true. operator could be a program that multiplies two numbers but only if they are both non-zero values.

Is isEmpty null safe?

6 Answers. No, absolutely not – because if acct is null, it won’t even get to isEmpty it will immediately throw a NullPointerException .

Where do I put javadoc comments?

The basic rule for creating JavaDoc comments is that they begin with /** and end with */….Adding JavaDoc comments

1. Immediately before the declaration of a public class.
2. Immediately before the declaration of a public field.
3. Immediately before the declaration of a public method or constructor.

What are invariants preconditions and postconditions?

Pre-conditions are the things that must be true before a method is called. The method tells clients “this is what I expect from you”. Post-conditions are the things that must be true after the method is complete. The method tells clients “this is what I promise to do for you”.

What does the checkargument of the preconditions class do?

The method checkArgument of the Preconditions class ensures the truthfulness of the parameters passed to the calling method. This method accepts a boolean condition and throws an IllegalArgumentException when the condition is false.

How are preconditions used in a static method?

Preconditions provide static methods to check that a method or a constructor is invoked with proper parameter or not. It checks the pre-conditions. Its methods throw IllegalArgumentException on failure.

What happens when false is passed to the preconditions method?

When false (or null) is passed instead, the Preconditions method throws an unchecked exception, which helps the calling method communicate to its caller that that caller has made a mistake. Example: In this example, checkArgument throws an IllegalArgumentException to indicate that exampleBadCaller made an error in its call to sqrt .

How does the checkstate method in guava work?

The method checkState checks the validity of the state of an object and is not dependent on the method arguments. For example, an Iterator might use this to check that next has been called before any call to remove.