Object Oriented Programming Week 10: Arrays

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Questions and Answers

What happens when an argument is passed by value in a method call?

  • The called method cannot modify the argument's data. (correct)
  • The original variable's value is modified directly.
  • Both the original and the copied values are modified.
  • A copy of the argument's value is created for the method. (correct)

Which of the following statements is true regarding pass-by-reference?

  • It does not improve performance when passing large data.
  • The called method can access and modify the original variable's value. (correct)
  • The called method works with a separate copy of the argument.
  • Pass-by-reference is always used for primitive data types.

What is a characteristic of multidimensional arrays?

  • They can only have two dimensions: rows and columns.
  • They are similar to tables with spots for rows and columns. (correct)
  • They are defined using a single row of values.
  • They cannot contain varying lengths of sub-arrays.

In which case can Java allow modification of an object's data when passing it to a method?

<p>When dealing with reference object types. (B)</p> Signup and view all the answers

How are two-dimensional arrays declared and initialized in Java?

<p>Using brackets to group the elements into rows. (A)</p> Signup and view all the answers

What type of variable can hold only one value at a time?

<p>Primitive type (B)</p> Signup and view all the answers

Which keyword is used to create an array in Java?

<p>new (B)</p> Signup and view all the answers

What will the expression 'c.length' return?

<p>The total number of elements in array c (A)</p> Signup and view all the answers

What does the term 'Pass-By-Reference' imply when passing arrays to methods?

<p>The method can modify the original array. (A)</p> Signup and view all the answers

In the expression 'c[a + b] += 2', what will it affect when 'a' is 5 and 'b' is 6?

<p>It will add 2 to element c[11]. (D)</p> Signup and view all the answers

Which statement is true regarding the index of an array?

<p>Index must be a positive integer or integer expression. (D)</p> Signup and view all the answers

What is the purpose of the finally statement in a try-catch block?

<p>To guarantee code execution after try-catch regardless of any exception. (D)</p> Signup and view all the answers

What does 'sum = c + c + c' imply about array c?

<p>It aggregates the values in all elements of c. (B)</p> Signup and view all the answers

What is the output when trying to print an array directly in Java?

<p>A reference to the array object is printed. (C)</p> Signup and view all the answers

What is the result of modifying an element in an array passed to a method using Pass-By-Value?

<p>The original array remains unchanged. (A)</p> Signup and view all the answers

What happens if an exception is thrown in the try block but not caught?

<p>The program terminates without executing the catch block. (D)</p> Signup and view all the answers

How do you pass an array to a method in Java?

<p>Use the array name directly without brackets. (C)</p> Signup and view all the answers

What type of loop does the enhanced for statement represent in Java?

<p>A loop designed to iterate through each element of an array. (A)</p> Signup and view all the answers

In which situation would you see the output 'Something went wrong.'?

<p>If an exception occurs within the try block. (B)</p> Signup and view all the answers

Why is it important to avoid stepping outside the array bounds?

<p>It prevents ArrayIndexOutOfBoundsException. (C)</p> Signup and view all the answers

What is an advantage of using an enhanced for statement?

<p>It eliminates the need for a loop counter and reduces errors. (C)</p> Signup and view all the answers

What is the correct way to declare and create an array of integers in Java?

<p>int[] c; c = new int[5]; (B)</p> Signup and view all the answers

Which of the following options correctly initializes two String arrays in a single declaration?

<p>String[] b, x = new String[]; (B)</p> Signup and view all the answers

What does the try-catch statement accomplish in Java?

<p>It allows handling of exceptions that might occur during execution. (B)</p> Signup and view all the answers

In the context of Java, what is the purpose of the catch statement within a try-catch block?

<p>To define the block of code that handles exceptions if they occur. (C)</p> Signup and view all the answers

What will happen if you run the following code: System.out.println(myNumbers); without proper indexing?

<p>It will raise an exception at runtime. (A)</p> Signup and view all the answers

How can an exception be defined within a Java program?

<p>As an indication of a problem during program execution. (D)</p> Signup and view all the answers

What is a common use of array initializers in Java?

<p>To directly assign values to an array during creation. (A)</p> Signup and view all the answers

Which of the following is NOT a valid syntax for initializing an array in Java?

<p>int nums[] = new int(3); (A)</p> Signup and view all the answers

Flashcards

Array Declaration

Declaring a variable that will hold an array of values of a specific data type. Example: int[] numbers;

Array Initialization

Assigning values to the array elements. Example: int[] numbers = {1, 2, 3};

Array Indexing

Accessing elements within the array using their position (index). The first element has index 0. Example: numbers[0] = 1;

Try-Catch

A programming structure in Java (and other languages) for handling possible errors (exceptions) during program execution.

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Exception

An error condition detected during program execution. Example: ArrayIndexOutOfBoundsException

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Try block

A section of code in a try-catch statement that is executed first. It includes the code that could produce an error.

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Catch block

A section of code in a try-catch statement that is executed if an error occurs in the try block.

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ArrayIndexOutOfBoundsException

An exception that occurs when attempting to access an array element using an invalid index.

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Primitive type variable

Holds one value of its type. When assigned a new value, the previous one is replaced.

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Reference type variable

Stores the memory address of an object. The variable is a pointer to the object's location in memory.

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Array length

The total number of elements an array can hold. Access it using the .length property.

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Modifying Arrays

Changing the value of an element within an array

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Pass-by-Value

A method receives a copy of the variable's value. Changes to the copy don't affect the original variable.

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Pass-by-Reference

A method call where the called method can directly access and modify the argument's value in the caller. This avoids copying data and improves performance.

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How are arguments passed in Java?

Java always uses pass-by-value. This means a copy of the argument is passed to the called method.

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What is a multidimensional array?

An array that represents data in a table form with rows and columns. Example: A two-dimensional array can store data for a spreadsheet.

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How can you declare a two-dimensional array?

Use double square brackets: int[][] b = {{1, 2}, {3, 4}}; Each inner array represents a row.

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Try-Catch Statement

A Java construct used to handle potential exceptions during program execution.

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finally statement

A block of code in a try-catch statement, always executed, regardless of errors, especially closing resources.

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Enhanced for loop

A loop in Java used to iterate over the elements of an array or collection, more readable than using indices.

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Passing Arrays to Methods

Methods can receive arrays as parameters. The array name, without brackets, is used in the method signature.

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Array

An ordered collection of elements of the same data type.

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Index

A numerical position used to access elements in an array (starting from zero).

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Study Notes

Course Information

  • Course: Object Oriented Programming
  • Institution: Saudi Electronic University
  • Week: 10
  • Topic: Arrays

Primitive vs. Reference Types

  • Primitive variables hold a single value of the declared type
  • Assigning a new value to a primitive variable replaces the previous one
  • Reference types store memory addresses of objects
  • A reference variable refers to an object, not the object's data itself

Creating, Initializing, and Modifying Arrays

  • Arrays store multiple data elements of the same type
  • Fixed-length data structures
  • Array size is determined when it’s created
  • Elements are accessed using index numbering, starting from 0

Exception Handling (Try-Catch Statements)

  • Exceptions indicate errors during program execution
  • Handle potential errors by placing error-prone code within a try block
  • Corresponding catch blocks handle the exception if it occurs

Enhanced for Statement

  • Iterates through array elements without a counter
  • Prevents the risk of going beyond array boundaries

Passing Arrays to Methods

  • Specify the array name in the method call
  • Pass-by-value—the method receives a copy of the values in the array; changes to the copy within the method will not affect the original array
  • Pass-by-reference—the method receives a refrence to the data; changes within the method will affect the original array

Pass-By-Value vs. Pass-By-Reference

  • Pass-by-value: A copy of the parameter is created, changes inside the method don't affect the original data in the calling method.
  • Pass-by-reference: The method receives a reference to the original data, changing the values in the method directly impacts the original values.

Multidimensional Arrays

  • Arrays with multiple levels of indices (e.g., tables with rows and columns)
  • Declaring a two-dimensional array example b[2][2]

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