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Quiz von Ben Wharnsby, aktualisiert more than 1 year ago
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Erstellt von Ben Wharnsby
vor fast 9 Jahre
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Frage 1
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Definition: Describes an object in Java. Objects are created from these. Blueprints for a type of object. What am i?
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Primitive Type
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Class
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Object
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Field
Frage 2
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An Object is a ...?
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Dynamic Entity, Created after constructor is invoked; collection of instance variables represent status.
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Shape, relationship and model.
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A value stored in associative memory.
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Blueprint of an class.
Frage 3
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Difference between Primitive and Reference types?
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Primitives are stored as status of objects and Reference types are stored in memory as values.
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Primitive types are stored in associative memory as a value; Reference types are stored in associative memory as an address of object state.
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No differences, both stored in associative memory.
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Both are dynamic entities.
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Difference between CLASS FIELD and INSTANCE VARIABLE?
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Fields are the types of data used in the class and an instance variable is used when a object is created allowing you to call the fields from a class.
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Fields in class definition specify types of data that consistute to the status of the object. Instance variables are created when the class constructor is invoked; an instance variable is set to each field.
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Class fields use the static modifier and are the types of data used in a class; instance variables allow you to reference data outside of a class.
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Class fields must always use the public modifier and instance variables are assigned to each field in the class on invoked.
Frage 5
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A Constructor contains a return type and starts with CAPITAL letters? True or False.
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- True
- False
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A method contains a Return type and by convention starts with lower case letters, addMoney(). True or False.
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- True
- False
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Which of these represents a Constant Identifier?
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final boolean public normal_working_week = 37.5;
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final boolean public NORMAL_WORKING_WEEK = 37.5;
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final DOUBLE NORMAL_WORKING_WEEK = 37.5;
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DOUBLE NORMAL_WORKING_WEEK = 37.5;
Frage 8
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What is a class variable?
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private static bookCount = 0; public Book { bookCount++; }
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private final bookCount = 0; public Book { bookCount++; }
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static private bookCount = 0; public Book { bookCount++; }
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private int bookCount = 0; public Book { bookCount++; }
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What is the sequence to create a count for True and False values?
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Create a fixed sized array. Initialise 'n' elements with the int 0. For loop to iterate through array, checking if the value is True or False. Increment index 0, by 1 if true; index 1 by 1, if false. Return new array, [1, 2];
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Initialise 'n' elements with the int 0. Create a fixed sized array. Increment index 0, by 1 if true; index 1 by 1, if false. For loop to iterate through array, checking if the value is True or False. Return new array, [1, 2];
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Initialise 'n' elements with the int 0. Create a fixed sized array. Create a arraylist of type boolean. Increment index 0, by 1 if true; index 1 by 1, if false. For loop to iterate through array, checking if the value is True or False. Return new array, [1, 2];
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Initialise 'n' elements with the int 0. Create a fixed sized array. Increment index 0, by 1 if true; index 1 by 1, if false. For loop to iterate through array, checking if the value is True or False. Return new array;
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Difference between an Array and an ArrayList?
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Array --> Fixed size, element can of only one type, but this type can be primitive/reference. ArrayList --> Variable size, elements can be reference types.
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Array --> Variable size, element can be any type, but this type can be primitive/reference. ArrayList --> Variable size, elements can be reference types.
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Array --> Variable size, element can be any type, but this type can be primitive/reference. ArrayList --> Fixed size, elements can be reference/primitive types.
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Array --> Fixed size, element can of only one type, but this type can be primitive/reference. ArrayList --> Variable size, elements can be reference/primitive types.
Frage 11
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ArrayList<BankAccount> currentAccounts = new ArrayList<BankAccount>();
Is this Correct?
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- True
- False
Frage 12
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Accessor methods --> Changes state of object by updating a value of instance variables.
Mutator methods --> Return information about the state of 'this' object. Doesn't change the value of a field.
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- True
- False
Frage 13
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public boolean sendToService() {
return lastService + serviceInterval <= mileage;
}
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- True
- False
Frage 14
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What is recursion?
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Process of a method calling another method.
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Process of a method calling itself.
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Process of a class calling another method.
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Process of a class calling itself.
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What are the 2 rules of Recursion?
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Must have at least 2 base classes + must ensure recursive calls eventually reach the base classes.
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Must have at least 1 base class + must ensure recursive calls eventually reach the base class.
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Must have at least 1 base class + must ensure recursive call at least one field in the class.
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Must have at least 1 base class + must ensure recursive calls contain more than one argument.
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Tail Recursion --> Where the return is the last operation that happens in recursion. True? False?
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- True
- False
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Recursive is better than Iterative, true or false?
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- True
- False
Frage 18
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What is an algorithm?
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A method in Java which is used to count the number of elements in an arrayList.
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Step by step process to solve a problem. Step by step instructions which termine and uses pseudo code.
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Step by step process to solve a problem. Step by step instructions which termine on a method and uses real code and Java statements.
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Step by step process to solve a linear search. Step by step instructions which termine on a method and uses real code, english and expressions.
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Worst-Case Complexity --> Maximum amount of computation used on an instance of a certain size. True or false?
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- True
- False
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SelectionSort Algorithm:
a = [a1, a2, ..., an]
k = 1
for i from 1 to (n - 1) do:
find item, next that should be in position 'i' in the sorted array.
swap items a, and next.
next = an (array reference);
indexOfNext = i;
for j from i+1 to n do:
if aj < next then:
next = aj
indexOfNext = j
endif
Is the complexity N^2?
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- True
- False
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Declare int indexOfNext and Comparable next;
For loop to iterate through array, but last element.
In for loop, assign next variable the current element and indexOfNext 'i'.
Still in for loop, do another for loop to iterate through all elements after current index, compare elements using compareTo() and assign next to a[j] and indexOfNext to 'j'; if next element is less than current element.
After 'j' for loop, a[indexOfNext] = a[i]; && a[i] = next; (Switch places).
Continue to loop!
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- True
- False
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Is this a correct statement?
Sorting.selectionSort(facebookFriends);
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- True
- False
Frage 23
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What is inheritance?
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Where a class implements another class or method. Features are inherited too.
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Where the subclass can inherit features and methods from another base class.
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Where the base class can inherit features and methods from another base class.
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Where the subclass can inherit only methods from another base class.
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Public class House extends Building {
private int numBedrooms;
public void setNumBedrooms(int a) {
numBedrooms = a;
}
}
Is this Inheritance?
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- True
- False
Frage 25
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What is the relationship between Building and House?
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Association
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Encapulsation
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Inheritance
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Dynamic Binding
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If we create a class, Street; what is it's relation to House?
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Association.
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Aggregation.
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Encapulsation
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Inheritance.
Frage 27
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public class Street {
...
}
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House[] houses; private String name; public Street(int b, String n) { name = n; houses = new House(b); }
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ArrayList<House> houses; private String name; public Street(int b, String n) { name = n; houses = new House(b); }
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ArrayList<House> houses; private String name; public Street(int b, String n) { name = n; houses = new House(b); name = b; }
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House[] houses; private Int name; public Street(int b, String n) { name = n; houses = new House(b); }
Frage 28
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Method Overriding?
Subclass changes it's behaviour of the baseclass, keeping the same method signature.
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- True
- False
Frage 29
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Polymorphism
A variable to hold just one reference to different types of classes.
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- True
- False
Frage 30
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Dynamic Binding
Operation to apply polymorphic variable is determined at runtime.
Depending on which class is currently assigned to a value (Account s), depends on which method is called.
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- True
- False
Frage 31
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What is an interface?
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Collection of methods and objects.
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Collection of abstract methods.
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Collection of methods.
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Collection of fields.
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Does a class that implement an interface have to implement all methods?
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- True
- False
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