Constructors - AP Computer Science A
Card 1 of 30
What happens if 'super()' is not explicitly called?
What happens if 'super()' is not explicitly called?
Tap to reveal answer
Java calls it automatically if not specified. Java inserts super() automatically if not explicitly written.
Java calls it automatically if not specified. Java inserts super() automatically if not explicitly written.
← Didn't Know|Knew It →
Which constructor type can be implicit?
Which constructor type can be implicit?
Tap to reveal answer
The default constructor. Java provides it automatically when no constructors exist.
The default constructor. Java provides it automatically when no constructors exist.
← Didn't Know|Knew It →
What does 'this()' aim to resolve?
What does 'this()' aim to resolve?
Tap to reveal answer
Constructor chaining within the same class. Enables code reuse between constructors in same class.
Constructor chaining within the same class. Enables code reuse between constructors in same class.
← Didn't Know|Knew It →
What is the main rule of constructor execution order?
What is the main rule of constructor execution order?
Tap to reveal answer
Base class constructors execute before derived class. Superclass initialization happens before subclass initialization.
Base class constructors execute before derived class. Superclass initialization happens before subclass initialization.
← Didn't Know|Knew It →
Identify the problem: class G extends H { G() {} }
Identify the problem: class G extends H { G() {} }
Tap to reveal answer
If H has no default constructor, error occurs. Depends on whether H has an accessible no-argument constructor.
If H has no default constructor, error occurs. Depends on whether H has an accessible no-argument constructor.
← Didn't Know|Knew It →
How is constructor inheritance handled in Java?
How is constructor inheritance handled in Java?
Tap to reveal answer
Constructors are not inherited in Java. Child classes must define their own constructors explicitly.
Constructors are not inherited in Java. Child classes must define their own constructors explicitly.
← Didn't Know|Knew It →
What is constructor delegation?
What is constructor delegation?
Tap to reveal answer
Using one constructor to call another in the same class. Reduces code duplication by calling other constructors.
Using one constructor to call another in the same class. Reduces code duplication by calling other constructors.
← Didn't Know|Knew It →
Find the issue: class F { F() { super(); } }
Find the issue: class F { F() { super(); } }
Tap to reveal answer
No issue if superclass has a default constructor. Explicit super() call is redundant but valid.
No issue if superclass has a default constructor. Explicit super() call is redundant but valid.
← Didn't Know|Knew It →
Which constructor is invoked first in inheritance?
Which constructor is invoked first in inheritance?
Tap to reveal answer
The parent class's constructor. Inheritance follows bottom-up constructor execution order.
The parent class's constructor. Inheritance follows bottom-up constructor execution order.
← Didn't Know|Knew It →
What is a copy constructor?
What is a copy constructor?
Tap to reveal answer
A constructor that creates a copy of an object. Takes another object as parameter to duplicate its state.
A constructor that creates a copy of an object. Takes another object as parameter to duplicate its state.
← Didn't Know|Knew It →
How can constructors enforce immutability?
How can constructors enforce immutability?
Tap to reveal answer
By initializing all fields and avoiding setters. Constructor sets final fields once, preventing later modification.
By initializing all fields and avoiding setters. Constructor sets final fields once, preventing later modification.
← Didn't Know|Knew It →
What is the syntax to call a constructor within another constructor?
What is the syntax to call a constructor within another constructor?
Tap to reveal answer
Use 'this()' with appropriate parameters. Must be the first statement and match parameter types.
Use 'this()' with appropriate parameters. Must be the first statement and match parameter types.
← Didn't Know|Knew It →
Identify the issue: class D { D() { this(5); } D(int y); }
Identify the issue: class D { D() { this(5); } D(int y); }
Tap to reveal answer
Missing constructor body for 'D(int y)'. Constructor declaration lacks implementation body with braces.
Missing constructor body for 'D(int y)'. Constructor declaration lacks implementation body with braces.
← Didn't Know|Knew It →
How does the JVM handle constructor absence?
How does the JVM handle constructor absence?
Tap to reveal answer
Provides a no-argument constructor by default. Only when no constructors are explicitly defined by programmer.
Provides a no-argument constructor by default. Only when no constructors are explicitly defined by programmer.
← Didn't Know|Knew It →
Which keyword is used to invoke a constructor?
Which keyword is used to invoke a constructor?
Tap to reveal answer
new. Creates a new object instance and calls the appropriate constructor.
new. Creates a new object instance and calls the appropriate constructor.
← Didn't Know|Knew It →
How do you declare a constructor in Java?
How do you declare a constructor in Java?
Tap to reveal answer
Same name as the class, no return type. Must match class name exactly and cannot have void or any return type.
Same name as the class, no return type. Must match class name exactly and cannot have void or any return type.
← Didn't Know|Knew It →
Find the issue: class C { C(int x) { this.x = x; } }
Find the issue: class C { C(int x) { this.x = x; } }
Tap to reveal answer
No default constructor; must provide 'x'. Default constructor is removed when parameterized constructor exists.
No default constructor; must provide 'x'. Default constructor is removed when parameterized constructor exists.
← Didn't Know|Knew It →
What happens if 'super()' is not explicitly called?
What happens if 'super()' is not explicitly called?
Tap to reveal answer
Java calls it automatically if not specified. Java inserts super() automatically if not explicitly written.
Java calls it automatically if not specified. Java inserts super() automatically if not explicitly written.
← Didn't Know|Knew It →
What is the role of 'super()' in a constructor?
What is the role of 'super()' in a constructor?
Tap to reveal answer
To call the parent class's constructor. Ensures parent class is properly initialized before child class.
To call the parent class's constructor. Ensures parent class is properly initialized before child class.
← Didn't Know|Knew It →
What is a parameterized constructor?
What is a parameterized constructor?
Tap to reveal answer
A constructor with parameters to initialize fields. Accepts arguments to set specific initial values for fields.
A constructor with parameters to initialize fields. Accepts arguments to set specific initial values for fields.
← Didn't Know|Knew It →
How do you differentiate a constructor from a method?
How do you differentiate a constructor from a method?
Tap to reveal answer
Constructors have no return type. Methods have return types; constructors initialize objects instead.
Constructors have no return type. Methods have return types; constructors initialize objects instead.
← Didn't Know|Knew It →
What happens if a constructor is private?
What happens if a constructor is private?
Tap to reveal answer
Object creation is limited to the class itself. Prevents external instantiation, used in singleton pattern.
Object creation is limited to the class itself. Prevents external instantiation, used in singleton pattern.
← Didn't Know|Knew It →
Identify the visibility modifier typically used for constructors.
Identify the visibility modifier typically used for constructors.
Tap to reveal answer
public. Allows objects to be created from outside the class.
public. Allows objects to be created from outside the class.
← Didn't Know|Knew It →
When is the default constructor provided?
When is the default constructor provided?
Tap to reveal answer
When no other constructors are defined. Java removes default constructor once any constructor is explicitly created.
When no other constructors are defined. Java removes default constructor once any constructor is explicitly created.
← Didn't Know|Knew It →
What is the default constructor?
What is the default constructor?
Tap to reveal answer
A no-argument constructor provided by Java. Automatically created by Java if no constructors are explicitly defined.
A no-argument constructor provided by Java. Automatically created by Java if no constructors are explicitly defined.
← Didn't Know|Knew It →
What happens if a constructor is private?
What happens if a constructor is private?
Tap to reveal answer
Object creation is limited to the class itself. Prevents external instantiation, used in singleton pattern.
Object creation is limited to the class itself. Prevents external instantiation, used in singleton pattern.
← Didn't Know|Knew It →
When is the default constructor provided?
When is the default constructor provided?
Tap to reveal answer
When no other constructors are defined. Java removes default constructor once any constructor is explicitly created.
When no other constructors are defined. Java removes default constructor once any constructor is explicitly created.
← Didn't Know|Knew It →
Which constructor is invoked first in inheritance?
Which constructor is invoked first in inheritance?
Tap to reveal answer
The parent class's constructor. Inheritance follows bottom-up constructor execution order.
The parent class's constructor. Inheritance follows bottom-up constructor execution order.
← Didn't Know|Knew It →
Find the issue: class F { F() { super(); } }
Find the issue: class F { F() { super(); } }
Tap to reveal answer
No issue if superclass has a default constructor. Explicit super() call is redundant but valid.
No issue if superclass has a default constructor. Explicit super() call is redundant but valid.
← Didn't Know|Knew It →
What is a constructor in Java?
What is a constructor in Java?
Tap to reveal answer
A special method to initialize objects. Called automatically when an object is created with 'new'.
A special method to initialize objects. Called automatically when an object is created with 'new'.
← Didn't Know|Knew It →