Refer to the following method, checkNumber, which checks the...

Refer to the following method, checkNumber, which checks the validity of its four-digit integer parameter.
A program invokes method checkNumber with the statement
Which of the following values of num will result in valid having a value of true?
(A) 6143
(B) 6144
(C) 6145
(D) 6146
(E) 6147

Key Concepts

Method Invocation and Parameter Passing

This concept involves how methods or functions are defined to accept inputs (parameters) and are later called (invoked) by passing appropriate arguments. Understanding how a method is invoked allows a programmer to know how data is transmitted into a procedure for processing and returning a result.

Input Validation

Input validation is the process of ensuring that the data provided to a program meets specific criteria before it is processed. This technique is commonly used in programming to prevent errors or unexpected behavior, such as verifying that an integer is indeed a four-digit number and checking if it adheres to predetermined rules.

Conditional Statements and Boolean Logic

Conditional statements use Boolean logic to evaluate whether certain conditions are met, determining the flow of a program. These constructs (such as if-else statements) enable a program to execute different code segments based on whether an expression is true or false, which is essential for checking the validity of data.

Arithmetic Operations and Digit Extraction

Arithmetic operations, including division and modulus, are fundamental for decomposing numbers into individual digits. This approach is important when validating numbers by checking the properties of each digit or comparing subsets of digits against specific rules.

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