找出下面代码中存在的错误。public class Test { public static void main(String[] arg

1.找出下面代码中存在的错误。public class Test { public static void main(String[] args) { m(new GraduateStudent()); m(new Student()); m(new Person()); m(new Object()); } public static void m(Student x) { System.out.println(x.toString()); }}class GraduateStudent extends Student {}class Student extends Person { @Override public String toString() { return "Student"; }}class Person extends Object { @Override public String toString() { return "Person"; }}

2.找出下面代码中存在的错误。 public class Test { public static void main(Stringargs) { m(new GraduateStudent()); m(new Student()); m(new Person()); m(new Object()); } public static void m(Student x) { System.out.println(x.toString()); } } class GraduateStudent extends Student { } class Student extends Person { @Override public String toString() { return "Student"; } } class Person extends Object { @Override public String toString() { return "Person"; } } 选项： A、m(new Student()) ,产生错误 B、m(new GraduateStudent()),产生错误 C、m(new Object()) ,产生错误 D、m(new Person()) ,产生错误

3.以下代码，查找编译错误。public class Test { public static void main(String[] args) { m(new GraduateStudent()); m(new Student()); m(new Person()); m(new Object()); } public static void m(Student x) { System.out.println(x.toString()); }} class GraduateStudent extends Student {} class Student extends Person { @Override public String toString() { return "Student"; }} class Person extends Object { @Override public String toString() { return "Person"; }}选项： A:m(new GraduateStudent()) 有错; B:m(new Student())有错; C:m(new Person()) 有错; D:m(new Object())有错

4.关于如下代码，下列选项正确的是（）class Test { public static void main(String[ ] args) { m(new GraduateStudent()); m(new Student()); m(new Person()); m(new Object()); } public static void m(Student x) { System.out.println(x.toString()); } } class GraduateStudent extends Student { } class Student extends Person { public String toString() { return "Student"; } } class Person extends Object { public String toString() { return "Person"; } }选项： A:m(new GraduateStudent()); 引起错误; B:m(new Person()) ;引起错误; C:m(new Object()); 引起错误; D:m(new Student()) ;引起错误

5.Given the following code, find the compile error. ( )Public class Test {Public static void main(String] args) {M(new GraduateStudent());M(new Student());M(new Person());M(new Object());}Public static void m(Student x) {System.out.println(x.toString());}}Class GraduateStudent extends Student {}Class Student extends Person {@OverridePublic String toString() {Return "Student";}}Class Person extends Object {@OverridePublic String toString() {Return "Person";} } 选项： A:m(new GraduateStudent()) causes an error B:m(new Student()) causes an error C:m(new Person()) causes an error D:m(new Object()) causes an error

6.阅读下列程序，并给出程序运行的结果。Public class PolymorphismDemo {Public static void main(String] args) { m(new GraduateStudent()); m(new Student()); m(new Person());} Public static void m(Object x) {System.out.println(x.toString());}} Class GraduateStudent extends Student {} Class Student extends Person {Public String toString() { return "I am a student";}} Class Person extends Object {Public String toString() { return "I am a person";}}

7.public class DynamicBindingDemo { public static void main(String[] args) { Object o = new GraduateStudent(); Object o1 = new Object(); if (o1 instanceof GraduateStudent) { System.out.println("Never got here"); GraduateStudent gs = (GraduateStudent)o1; } m(o); m(new Student()); m(new Person()); m(new Object()); } public static void m( 【1】 ) { System.out.println(x.toString()); }} class GraduateStudent extends Student {}class Student extends Person { public String toString() { return "Student"; }}class Person extends Object { public String toString() { return "Person"; }}

8.分析下列代码，找出编译错误（本题为多选） public class Test { public static void main(String[ ] args) { m(new GraduateStudent()); m(new Student()); m(new Person()); m(new Object()); } public static void m(Student x) { System.out.println(x.toString()); } } class GraduateStudent extends Student { } class Student extends Person { public String toString() { return "Student"; } } class Person extends Object { public String toString() { return "Person"; } } 选项： A、m(new Object()) 会导致编译错误 B、m(new Student()) 会导致编译错误 C、m(new GraduateStudent()) 会导致编译错误 D、m(new Person()) 会导致编译错误

9.下列代码的输出是什么?public class Test { public static void main(String[] args) { new Person().printPerson(); new Student().printPerson(); }} class Student extends Person { public String getInfo() { return "Student"; }} class Person { public String getInfo() { return "Person"; } public void printPerson() { System.out.println(getInfo()); }}选项： A:Person Person; B:Person Student; C:Stduent Student; D:Student Person

10.What is the output of the following code? ( )Public class Test {Public static void main(String] args) {New Person().printPerson();New Student().printPerson();}}Class Student extends Person {Private String getInfo() {Return "Student";}}Class Person {Private String getInfo() {Return "Person";}Public void printPerson() {System.out.println(getInfo());} } 选项： A:Person Person B:Person Student C:Stduent Student D:Student Person

11. 单选题What is the output of the following code? ( )Public class Test {Public static void main(String] args) {New Person().printPerson();New Student().printPerson();}}Class Student extends Person {@OverridePublic String getInfo() {Return "Student";}}Class Person {Public String getInfo() {Return "Person";}Public void printPerson() {System.out.println(getInfo());}} 选项： A:Person Person B:Person Student C:Stduent Student D:Student Person

12.下列代码的输出是什么public class Test { public static void main(String[] args) { new Person().printPerson(); new Student().printPerson(); }} class Student extends Person { private String getInfo() { return "Student"; }} class Person { private String getInfo() { return "Person"; } public void printPerson() { System.out.println(getInfo()); }}选项： A:Person Person; B:Person Student; C:Stduent Student; D:Student Person

13. 单选题What is the output of the following code? ( )Public class Test {Public static void main(String] args) {New Person().printPerson();New Student().printPerson();}}Class Student extends Person {Private String getInfo() {Return "Student";}}Class Person {Private String getInfo() {Return "Person";}Public void printPerson() {System.out.println(getInfo());}} 选项： A:Person Person B:Person Student C:Stduent Student D:Student Person

14.已知: public class C{ public static void main(Stringfargs){ print(newGraduateStudentQ): } public static void print(Object x){ Systemout.println(xtoStringQ): } } class Person{ public String toStringO{ retumPerson"; } } class Student extends Person{ public String toStringQ{ retum"Student"; } } class GraduateStudent extends Student{ } 则输出为: 选项： A:GraduateStudent B:Student C:Person D:Object

15.编译运行如下java代码，输出结果是（）class Person{ String name = "person"; public void shout(){ System.out.print(name); }}class Student extends Person{ String name = "student"; String school = "school";} public class Test{ public static void main(String[] args){ Person p = new Student(); p.shout(); }}选项： A: person ; B:student ; C:person student ; D:编译错误

16.编译运行如下java代码，输出结果是（） class Person{ String name = "person"; public void shout(){ System.out.print(name); } } class Student extends Person{ String name = "student"; String school = "school"; } public class Test{ public static void main(String[] args){ Person p = new Student(); p.shout(); } } 选项： A、person B、student C、person student D、编译错误

17.编译运行如下代码，输出结果是（）。Class Person {String name=”person”;public void shout(){System.out.prinnt(name);}}Class Student extends person{String name=”student”;Student school=”school”;}Class Text {public static void main(String [] args){Person p=new Student();p.shout();}} 选项： A、person B、student C、person D、编译错误

(s); } }public class Person{ public int ID { get; set; } public string Name { get; set; } public static void PromptName(T t) where T : Person { Console.WriteLine(t); } }程序运行结果">18.阅读下面程序段class Student : Person{ public override string ToString() { return ID + "\t" + Name; } static void Main() { Student s = new Student(); s.ID = 1; s.Name = "JSON"; PromptName(s); } }public class Person{ public int ID { get; set; } public string Name { get; set; } public static void PromptName(T t) where T : Person { Console.WriteLine(t); } }程序运行结果

19.请写出下面程序的输出结果。class Person { 　　 public void m() { System.out.println(“I am in Person.”); } 　 } 　 public class Teacher extends Person { 　　 public void m() { System.out.println(“I am in Teacher.”); } 　　 public static void main(String args[]){ 　　 Person t = new Teacher(); 　 t.m(); 　　 }}

20.以下程序的输出结果是？class Person{String name="person";public void shout(){System.out.print(name);}}class Student extends Person{String name="student";String school="school";}class Test{public static void main(String[] args){Person p=new Student();System.out.print(p instanceof Student);System.out.print(p instanceof Person);System.out.print(p instanceof Object);System.out.print(p instanceof System);}}

21.【填空题】23. import java.text.*; public class Java_2 { public static void main(String[] args) { Person[] people = new Person[2]; people[0] = new Worker("老张", 30000); people[1] = new Student("小王", "计算机科学"); for (int i = 0; i < people.length; i++) { Person p = people[i]; //*********Found********** System.out.println(____________________() + ", " + p.getDescription()); } } } //*********Found********** ________________ class Person { public Person(String n) { name = n; } //*********Found********** public ___________________ String getDescription(); public String getName() { return name; } private String name; } //*********Found********** class Worker _________________ Person { public Worker(String n, double s) { super(n); salary = s; } public String getDescription() { NumberFormat formatter = NumberFormat.getCurrencyInstance(); return "工人，年薪是 " + formatter.format(salary) + "。"; } private double salary; } //*********Found********** class Student _________________ Person { public Student(String n, String m) { super(n); major = m; } public String getDescription() { return "学生，专业是 " + major + "。"; } private String major; }

22.对于static函数，子类加了相同的函数，输出是？class M { public static void output() { System.out.println("M"); }}class N extends M { public static void output() { System.out.println("N"); }}public class StaticTest { public static void main(String[] args) { M m = new N(); m.output(); }

23. 下列代码的输出结果是（）class Father{int m=100;public int setM(){return m;}}class Son extends Father{int m=6;public int setM(){return m;}}public class E{public static void main(String args[]){Sonobj=new Son();System.out.println(son.setM());}}

24.下列Java代码中Test类中的四个输出语句的输出结果依次是(　　) Class Person{ String name=”person”; public void shout(){ System.out.println(name); } } class Student extends Person{ String name=”student”; String school=”school”; } Class Test{ public static void main (String[] args ){ Person p=new Student(); System.out.print(p instanceof Student); System.out.print(p instanceof Person); System.out.print(p instanceof Object); System.out.print(p instanceof System); } } 选项：A、true,false,true,falseB、false,true,false,falseC、true,true,true,D、true,,true,false,编译错误