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Questions and Answers
What keyword is used to declare a new array in programming?
What keyword is used to declare a new array in programming?
- array
- create
- define
- new (correct)
What will the first index of an array always be?
What will the first index of an array always be?
- 2
- 0 (correct)
- 1
- -1
What is the default value of elements in a new String array when using the new method?
What is the default value of elements in a new String array when using the new method?
- null (correct)
- zero
- empty string
- undefined
What is an example of a perfect size array?
What is an example of a perfect size array?
What occurs when you attempt to store an int in a String array?
What occurs when you attempt to store an int in a String array?
What does it mean when an array is said to be a 'perfect size' array?
What does it mean when an array is said to be a 'perfect size' array?
How are perfect size arrays passed to methods in programming?
How are perfect size arrays passed to methods in programming?
Which of the following describes the use of initializer lists in array creation?
Which of the following describes the use of initializer lists in array creation?
What does the term 'indices' refer to in the context of an array?
What does the term 'indices' refer to in the context of an array?
What default value does an integer array initialize its elements to when using the 'new' method?
What default value does an integer array initialize its elements to when using the 'new' method?
What will be the output when printing an array without specifying an index?
What will be the output when printing an array without specifying an index?
Which of the following is a common error when working with arrays?
Which of the following is a common error when working with arrays?
How would you modify an element in an array?
How would you modify an element in an array?
What happens to a String array when initialized using the 'new' method?
What happens to a String array when initialized using the 'new' method?
What is the final output when the cars ArrayList is processed?
What is the final output when the cars ArrayList is processed?
What will happen if grades.set(0, 42) is added after grades.add(98);?
What will happen if grades.set(0, 42) is added after grades.add(98);?
If you attempt to access an index that is out of range for an array, what is typically the result?
If you attempt to access an index that is out of range for an array, what is typically the result?
What does the following code snippet print: System.out.println(double[] decimals = new double)?
What does the following code snippet print: System.out.println(double[] decimals = new double)?
Which of the following would correctly modify the code to find the maximum grade?
Which of the following would correctly modify the code to find the maximum grade?
What is the purpose of the line letters.remove(0) in the reversing code?
What is the purpose of the line letters.remove(0) in the reversing code?
Why is an enhanced for loop suitable for finding the minimum grade?
Why is an enhanced for loop suitable for finding the minimum grade?
What will the output be after reversing the letters ArrayList?
What will the output be after reversing the letters ArrayList?
What is the initial value of min before searching for the minimum grade?
What is the initial value of min before searching for the minimum grade?
What is a key difference between the methods used to find the minimum and maximum grades?
What is a key difference between the methods used to find the minimum and maximum grades?
What is the primary purpose of a 2D array?
What is the primary purpose of a 2D array?
When defining a 2D array, which syntax correctly initializes a 2D array with 3 rows and 2 columns?
When defining a 2D array, which syntax correctly initializes a 2D array with 3 rows and 2 columns?
Which statement correctly accesses the element in the second row and third column of a 2D array named 'data'?
Which statement correctly accesses the element in the second row and third column of a 2D array named 'data'?
What is the correct way to print the number of columns in the first row of a 2D array named 'records'?
What is the correct way to print the number of columns in the first row of a 2D array named 'records'?
What does the following code snippet do: 'System.out.println(names.length + " rows");'?
What does the following code snippet do: 'System.out.println(names.length + " rows");'?
What technique is commonly used to populate a 2D array during its declaration?
What technique is commonly used to populate a 2D array during its declaration?
How do you iterate through a 2D array using a regular for loop?
How do you iterate through a 2D array using a regular for loop?
Which of the following statements about 2D arrays is false?
Which of the following statements about 2D arrays is false?
What are 'formal parameters' in the context of a constructor?
What are 'formal parameters' in the context of a constructor?
Which method call would move the turtle backward by 10 pixels?
Which method call would move the turtle backward by 10 pixels?
What happens when a method call is executed in a program?
What happens when a method call is executed in a program?
In the constructor example provided, what do (300,300) represent?
In the constructor example provided, what do (300,300) represent?
What is indicated by the term 'call by value'?
What is indicated by the term 'call by value'?
Which of the following methods is used to change the color of the turtle?
Which of the following methods is used to change the color of the turtle?
What is the effect of a method's return value on control flow?
What is the effect of a method's return value on control flow?
Which statement correctly describes how programmers interact with methods?
Which statement correctly describes how programmers interact with methods?
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Study Notes
Working with ArrayLists
- ArrayList Creation: Initialize an ArrayList with
ArrayList cars = new ArrayList(); - Element Addition: Use
cars.add(element)to add elements like "Corolla", "Camry", "Prius", etc. - Element Availability Check: Use an enhanced for loop to determine if a specific element (e.g., "Prius") is available and update a string accordingly.
- Printing Elements: Print the status of availability using
System.out.println(Prius);.
Finding Minimum and Maximum Values
- Finding Minimum: Set initial
minto the first element of the grades ArrayList. Loop through elements and updateminif a smaller value is found. - Finding Maximum: Similar to minimum, initialize
maxand check for larger values during iteration. - Enhanced for Loop: Utilizes a simpler syntax for iterating through collections.
Reversing ArrayList Elements
- Element Access: Use regular for loops in reverse order to add elements back into the ArrayList.
- Element Removal: Remove original elements from the ArrayList to keep only the reversed elements.
- Index Management: Important to use
remove(0)to continuously access the first element without skipping any.
Array Basics
- Declaration: Declare an array with a name followed by
newand defined data type (e.g.,String[] names = new String[5];). - Default Values: New arrays automatically initialize to default values (null for strings, 0 for integers).
- Array Indices: Start at 0; trying to access out-of-bounds results in
ArrayIndexOutOfBoundsException.
Perfect Size Arrays
- Definition: A perfect size array has a number of elements equal to the allocated memory.
- Usage: Ideal for fixed data, such as days of the week where the size won’t change.
- Array Method Parameters: Pass by reference, indicating the location in memory rather than the contents.
Modifying and Accessing Arrays
- Element Modification: Access array elements using their index to assign new values.
- 2D Arrays: Defined with two sets of brackets (e.g.,
String[][] names = new String[rows][columns];). - Accessing in 2D Arrays: Use two indices to access and manipulate element positions within the array.
Array Method Calls
- Method Functionality: Methods define behaviors for objects, including how to manipulate variables or perform actions.
- Control Flow: Method calls interrupt sequence, executing all statements in the method before resuming.
Turtle Class Example
- Method Examples: Methods like
forward(),backward(),right(), andleft()control the movement of a Turtle object. - Understanding Methods: Programmers can utilize methods without understanding their implementation, focusing on input-output behavior instead.
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