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单选题
Given the uncompleted code of a class: class Person { String name, department; int age; public Person(String n){ name = n; } public Person(String n, int a){ name = n; age = a; } public Person(String n, String d, int a) { // doing the same as two arguments version of constructor // including assignment name=n,age=a department = d; } } Which expression can be added at the "doing the same as..." part of the constructor?()
A
Person(n,a);
B
this(Person(n,a));
C
this(n,a);
D
this(name,age);
参考答案
参考解析
解析:
在同一个类的不同构造方法中调用该类的其它构造方法需要使用this(…)的形式,而且必须是在构造方法的第一行调用,这个和普通的方法重载调用的方式不同,普通的方法可以直接使用方法名加参数来调用,而且调用位置没有限制,因此答案A是不行的,B的语法就是错误的,D的错误在于在父类型的构造函数被调用前不能引用类的成员。构造方法是一个类对象实例化的起点(虽然严格来说首先执行的并不是构造方法的第一个语句,而是内存的分配),因此在构造方法中不能将成员作为参数引用。
更多 “单选题Given the uncompleted code of a class: class Person { String name, department; int age; public Person(String n){ name = n; } public Person(String n, int a){ name = n; age = a; } public Person(String n, String d, int a) { // doing the same as two arguments version of constructor // including assignment name=n,age=a department = d; } } Which expression can be added at the "doing the same as..." part of the constructor?()A Person(n,a);B this(Person(n,a));C this(n,a);D this(name,age);” 相关考题
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Given the uncompleted code of a class: class Person { String name, department; int age; public Person(String n){ name = n; } public Person(String n, int a){ name = n; age = a; } public Person(String n, String d, int a) { // doing the same as two arguments version of constructor // including assignment name=n,age=a department = d; } } Which expression can be added at the "doing the same as..." part of the constructor?() A、 Person(n,a);B、 this(Person(n,a));C、 this(n,a);D、 this(name,age);
考题
11. class Person { 12. String name = “No name‟; 13. public Person(String nm) { name = nm; } 14. } 15. 16. class Employee extends Person { 17. String emplD = “0000”; 18. public Employee(String id) { empID = id; } 19. } 20. 21. public class EmployeeTest { 22. public static void main(String[] args) { 23. Employee e = new Employee(”4321”); 24. System.out.println(e.empID); 25. } 26. } What is the result?() A、 4321B、 0000C、 An exception is thrown at runtime.D、 Compilation fails because of an error in line 18.
考题
多选题Which are syntactically valid statement at// point x?() class Person { private int a; public int change(int m){ return m; } } public class Teacher extends Person { public int b; public static void main(String arg[]){ Person p = new Person(); Teacher t = new Teacher(); int i; // point x } }Ai = m;Bi = b;Ci = p.a;Di = p.change(30);Ei = t.b.
考题
单选题11. class Person { 12. String name = “No name‟; 13. public Person(String nm) { name = nm; } 14. } 15. 16. class Employee extends Person { 17. String emplD = “0000”; 18. public Employee(String id) { empID = id; } 19. } 20. 21. public class EmployeeTest { 22. public static void main(String[] args) { 23. Employee e = new Employee(”4321”); 24. System.out.println(e.empID); 25. } 26. } What is the result?()A
4321B
0000C
An exception is thrown at runtime.D
Compilation fails because of an error in line 18.
考题
单选题public class Employee{ private String name; public Employee(String name){ this.name = name; } public String getName(){ return name; } } public class Manager extends Employee{ private String department; public Manager(String name,String department){ this.department = department; super(name); System.out.println(getName()); } } 执行语句new Manager(“smith”,”SALES”)后程序的输出是哪项?()A
smithB
nullC
SALESD
编译错误
考题
单选题public class Person { private name; public Person(String name) { this.name = name; } public int hashCode() { return 420; } } Which is true?()A
The time to find the value from HashMap with a Person key depends on the size of the map.B
Deleting a Person key from a HashMap will delete all map entries for all keys of typePerson.C
Inserting a second Person object into a HashSet will cause the first Person object to beremoved as a duplicate.D
The time to determine whether a Person object is contained in a HashSet is constant and does NOT depend on the size of the map.
考题
单选题public class Person { private String name, comment; private int age; public Person(String n, int a, String c) { name = n; age = a; comment = c; } public boolean equals(Object o) { if(! (o instanceof Person)) return false; Person p = (Person)o; return age == p.age name.equals(p.name); } } What is the appropriate definition of the hashCode method in class Person?()A
return super.hashCode();B
return name.hashCode() + age * 7;C
return name.hashCode() + comment.hashCode() /2;D
return name.hashCode() + comment.hashCode() / 2 - age * 3;
考题
单选题Given the uncompleted code of a class: class Person { String name, department; int age; public Person(String n){ name = n; } public Person(String n, int a){ name = n; age = a; } public Person(String n, String d, int a) { // doing the same as two arguments version of constructor // including assignment name=n,age=a department = d; } } Which expression can be added at the "doing the same as..." part of the constructor?()A
Person(n,a);B
this(Person(n,a));C
this(n,a);D
this(name,age);
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