What this deck covers
This deck focuses on Constructors, giving you a quick way to review the definitions, rules, and examples that matter most for AP Computer Science a.
AP Computer Science a Flashcards: Constructors
Study Constructors in AP Computer Science a with focused flashcards that help you recognize the idea, recall the key rule, and apply it in practice-style prompts.
AP Computer Science a
Constructors
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QUESTION
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When is the default constructor provided?
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ANSWER
When no other constructors are defined. Java removes default constructor once any constructor is explicitly created.
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Flashcard 1: When is the default constructor provided?
Answer: When no other constructors are defined. Java removes default constructor once any constructor is explicitly created.
Flashcard 2: Find the issue: class C { C(int x) { this.x = x; } }
Answer: No default constructor; must provide 'x'. Default constructor is removed when parameterized constructor exists.
Flashcard 3: When is the default constructor provided?
Answer: When no other constructors are defined. Java removes default constructor once any constructor is explicitly created.
Flashcard 4: Which constructor is invoked first in inheritance?
Answer: The parent class's constructor. Inheritance follows bottom-up constructor execution order.
Flashcard 5: How are static fields initialized in constructors?
Answer: Static fields are not initialized in constructors. Static fields belong to class, initialized once at class loading.
Flashcard 6: Find the issue: class F { F() { super(); } }
Answer: No issue if superclass has a default constructor. Explicit super() call is redundant but valid.
Flashcard 7: What happens if 'super()' is not explicitly called?
Answer: Java calls it automatically if not specified. Java inserts super() automatically if not explicitly written.
Flashcard 8: Find the error: class I { I(String str) {} I() { this(str); } }
Answer: 'str' is not accessible in 'I()'. Local parameter 'str' from other constructor is not accessible.
Flashcard 9: Identify the visibility modifier typically used for constructors.
Answer: public. Allows objects to be created from outside the class.
Flashcard 10: How is constructor inheritance handled in Java?
Answer: Constructors are not inherited in Java. Child classes must define their own constructors explicitly.
Flashcard 11: What is the syntax to call a constructor within another constructor?
Answer: Use 'this()' with appropriate parameters. Must be the first statement and match parameter types.
Flashcard 12: What is constructor delegation?
Answer: Using one constructor to call another in the same class. Reduces code duplication by calling other constructors.
Flashcard 13: What is constructor overloading?
Answer: Multiple constructors with different parameters. Provides flexibility for different initialization scenarios.
Flashcard 14: What does 'this()' aim to resolve?
Answer: Constructor chaining within the same class. Enables code reuse between constructors in same class.
Flashcard 15: How does the JVM handle constructor absence?
Answer: Provides a no-argument constructor by default. Only when no constructors are explicitly defined by programmer.
Flashcard 16: Which keyword is used to invoke a constructor?
Answer: new. Creates a new object instance and calls the appropriate constructor.
Flashcard 17: Identify the issue: class J { J(int k) {} J(double k) {} }
Answer: No issue; this is constructor overloading. Different parameter types allow valid constructor overloading.
Flashcard 18: How does constructor chaining work?
Answer: Using 'this()' to call another constructor in the same class. Must be the first statement in the constructor body.
Flashcard 19: What is a constructor in Java?
Answer: A special method to initialize objects. Called automatically when an object is created with 'new'.
Flashcard 20: Which keyword is used to invoke a constructor?
Answer: new. Creates a new object instance and calls the appropriate constructor.
Flashcard 21: Identify the error: class A { A() {} void A() {} }
Answer: Method 'void A()' cannot be a constructor. Constructors cannot have return types, including void.
Flashcard 22: What is a copy constructor?
Answer: A constructor that creates a copy of an object. Takes another object as parameter to duplicate its state.
Flashcard 23: How does constructor chaining work?
Answer: Using 'this()' to call another constructor in the same class. Must be the first statement in the constructor body.
Flashcard 24: Which constructor is invoked first in inheritance?
Answer: The parent class's constructor. Inheritance follows bottom-up constructor execution order.
Flashcard 25: Which constructor type can be implicit?
Answer: The default constructor. Java provides it automatically when no constructors exist.
Flashcard 26: When is 'super()' required in a constructor?
Answer: When the parent class has no default constructor. Must explicitly call parameterized parent constructor with super().
Flashcard 27: Identify the visibility modifier typically used for constructors.
Answer: public. Allows objects to be created from outside the class.
Flashcard 28: What is the effect of constructor overloading?
Answer: Allows different initialization scenarios. Multiple ways to create objects with different initial states.
Flashcard 29: How do you declare a constructor in Java?
Answer: Same name as the class, no return type. Must match class name exactly and cannot have void or any return type.
Flashcard 30: How are static fields initialized in constructors?
Answer: Static fields are not initialized in constructors. Static fields belong to class, initialized once at class loading.
Flashcard 31: What is a parameterized constructor?
Answer: A constructor with parameters to initialize fields. Accepts arguments to set specific initial values for fields.
Flashcard 32: What is the default constructor?
Answer: A no-argument constructor provided by Java. Automatically created by Java if no constructors are explicitly defined.
Flashcard 33: Find the issue: class C { C(int x) { this.x = x; } }
Answer: No default constructor; must provide 'x'. Default constructor is removed when parameterized constructor exists.
Flashcard 34: What is the role of 'super()' in a constructor?
Answer: To call the parent class's constructor. Ensures parent class is properly initialized before child class.
Flashcard 35: What is the effect of constructor overloading?
Answer: Allows different initialization scenarios. Multiple ways to create objects with different initial states.
Flashcard 36: Identify the problem: class G extends H { G() {} }
Answer: If H has no default constructor, error occurs. Depends on whether H has an accessible no-argument constructor.
Flashcard 37: What is a parameterized constructor?
Answer: A constructor with parameters to initialize fields. Accepts arguments to set specific initial values for fields.
Flashcard 38: Find the issue: class F { F() { super(); } }
Answer: No issue if superclass has a default constructor. Explicit super() call is redundant but valid.
Flashcard 39: Identify the issue: class J { J(int k) {} J(double k) {} }
Answer: No issue; this is constructor overloading. Different parameter types allow valid constructor overloading.
Flashcard 40: What happens if 'super()' is not explicitly called?
Answer: Java calls it automatically if not specified. Java inserts super() automatically if not explicitly written.
Flashcard 41: What is the primary function of a constructor block?
Answer: To execute code for every new object instance. Runs initialization code every time an object is instantiated.
Flashcard 42: What does 'this()' aim to resolve?
Answer: Constructor chaining within the same class. Enables code reuse between constructors in same class.
Flashcard 43: Which constructor type can be implicit?
Answer: The default constructor. Java provides it automatically when no constructors exist.
Flashcard 44: What happens if a constructor is private?
Answer: Object creation is limited to the class itself. Prevents external instantiation, used in singleton pattern.
Flashcard 45: What is the main rule of constructor execution order?
Answer: Base class constructors execute before derived class. Superclass initialization happens before subclass initialization.
Flashcard 46: Identify the problem: class G extends H { G() {} }
Answer: If H has no default constructor, error occurs. Depends on whether H has an accessible no-argument constructor.
Flashcard 47: What is constructor overloading?
Answer: Multiple constructors with different parameters. Provides flexibility for different initialization scenarios.
Flashcard 48: How does the JVM handle constructor absence?
Answer: Provides a no-argument constructor by default. Only when no constructors are explicitly defined by programmer.
Flashcard 49: What happens if a constructor is private?
Answer: Object creation is limited to the class itself. Prevents external instantiation, used in singleton pattern.
Flashcard 50: Find the error: class I { I(String str) {} I() { this(str); } }
Answer: 'str' is not accessible in 'I()'. Local parameter 'str' from other constructor is not accessible.
Flashcard 51: What is the primary function of a constructor block?
Answer: To execute code for every new object instance. Runs initialization code every time an object is instantiated.
Flashcard 52: Identify the use of the 'this' keyword in constructors.
Answer: To refer to the current object's fields. Resolves naming conflicts between parameters and instance variables.
Flashcard 53: What is constructor delegation?
Answer: Using one constructor to call another in the same class. Reduces code duplication by calling other constructors.
Flashcard 54: How is constructor inheritance handled in Java?
Answer: Constructors are not inherited in Java. Child classes must define their own constructors explicitly.
Flashcard 55: When is 'super()' required in a constructor?
Answer: When the parent class has no default constructor. Must explicitly call parameterized parent constructor with super().
Flashcard 56: What is a copy constructor?
Answer: A constructor that creates a copy of an object. Takes another object as parameter to duplicate its state.
Flashcard 57: What is the syntax to call a constructor within another constructor?
Answer: Use 'this()' with appropriate parameters. Must be the first statement and match parameter types.
Flashcard 58: Which class member is initialized using a constructor?
Answer: Instance variables. Object fields that store the state of each instance.
Flashcard 59: Identify the error: class A { A() {} void A() {} }
Answer: Method 'void A()' cannot be a constructor. Constructors cannot have return types, including void.
Flashcard 60: How do you differentiate a constructor from a method?
Answer: Constructors have no return type. Methods have return types; constructors initialize objects instead.
Flashcard 61: How do you differentiate a constructor from a method?
Answer: Constructors have no return type. Methods have return types; constructors initialize objects instead.
Flashcard 62: Identify the issue: class D { D() { this(5); } D(int y); }
Answer: Missing constructor body for 'D(int y)'. Constructor declaration lacks implementation body with braces.
Flashcard 63: What is the default constructor?
Answer: A no-argument constructor provided by Java. Automatically created by Java if no constructors are explicitly defined.
Flashcard 64: Identify the use of the 'this' keyword in constructors.
Answer: To refer to the current object's fields. Resolves naming conflicts between parameters and instance variables.
Flashcard 65: How do you declare a constructor in Java?
Answer: Same name as the class, no return type. Must match class name exactly and cannot have void or any return type.
Flashcard 66: How can constructors enforce immutability?
Answer: By initializing all fields and avoiding setters. Constructor sets final fields once, preventing later modification.
Flashcard 67: What is the role of 'super()' in a constructor?
Answer: To call the parent class's constructor. Ensures parent class is properly initialized before child class.
Flashcard 68: Identify the purpose of a constructor.
Answer: To initialize an object's fields. Sets initial values for instance variables when object is created.
Flashcard 69: How can constructors enforce immutability?
Answer: By initializing all fields and avoiding setters. Constructor sets final fields once, preventing later modification.
Flashcard 70: What is the main rule of constructor execution order?
Answer: Base class constructors execute before derived class. Superclass initialization happens before subclass initialization.
Flashcard 71: Identify the issue: class D { D() { this(5); } D(int y); }
Answer: Missing constructor body for 'D(int y)'. Constructor declaration lacks implementation body with braces.
Flashcard 72: Which class member is initialized using a constructor?
Answer: Instance variables. Object fields that store the state of each instance.