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1、JAVA語(yǔ)言基礎(chǔ)筆試題-1
Question 1 (43)
Given:
1. class TestA {
2. public void start() { System.out.println(”TestA”); }
3. }
4. public class TestB extends TestA {
5. public void start() { System.out.println(”TestB”); }
6. public static void main
2、(String[] args) {
7. ((TestA)new TestB()).start(); // TestA x=new TestB(); x.start();
8. }
9. }
What is the result?
A. TestA
B. TestB
C. Compilation fails.
D. An exception is thrown at runtime.
答案：B
考點(diǎn)：繼承環(huán)境下，父類(lèi)引用變量指向子類(lèi)的問(wèn)題。
說(shuō)明：繼承環(huán)境下，父類(lèi)引用變量指向子類(lèi)對(duì)象時(shí)調(diào)用的方法應(yīng)從子類(lèi)先找，如果子類(lèi)沒(méi)有找到再?gòu)母割?lèi)中查找。
Question 2
3、
Given:
1. interface TestA { String toString(); }
2. public class Test {
3. public static void main(String[] args) {
4. System.out.println(new TestA() {
5. public String toString() { return “test”; }
6. });
7. }
8. }
What is the result?
A. test
B. null
C. An exception is thrown at runtim
4、e.
D. Compilation fails because of an error in line 1.
E. Compilation fails because of an error in line 4.
F. Compilation fails because of an error in line 5.
答案：A
考點(diǎn)：接口的考察。
說(shuō)明：本體在輸出語(yǔ)句中直接創(chuàng)建TestA的對(duì)象，并在語(yǔ)句中完成并且調(diào)用toString（）方法。
Question 3
Given:
11. public abstract class Shape {
12. int x;
1
5、3. int y;
14. public abstract void draw();
15. public void setAnchor(int x, int y) {
16. this.x = x;
17. this.y = y;
18. }
19. }
and a class Circle that extends and fully implements the Shape class.
Which is correct?
A. Shape s = new Shape();
s.setAnchor(10,10);
s.draw();
B. Circle c = n
6、ew Shape();
c.setAnchor(10,10);
c.draw();
C. Shape s = new Circle();
s.setAnchor(10,10);
s.draw();
D. Shape s = new Circle();
s->setAnchor(10,10);
s->draw();
E. Circle c = new Circle();
c.Shape.setAnchor(10,10);
c.Shape.draw();
答案：B
考點(diǎn)：考察子類(lèi)繼承和抽象類(lèi)的問(wèn)題。
說(shuō)明：在繼承和抽象類(lèi)中，子類(lèi)對(duì)象不能調(diào)用父類(lèi)的方法，當(dāng)父類(lèi)引用變量指向
7、之類(lèi)對(duì)行時(shí)，指代的是父類(lèi)的部分，不能調(diào)用子類(lèi)的方法。抽象類(lèi)中未完成的放法不能被調(diào)用，只有完成了方法才能被調(diào)用。
Question 4
Given:
10. abstract public class Employee {
11. protected abstract double getSalesAmount();
12. public double getCommision() {
13. return getSalesAmount() * 0.15;
14. }
15. }
16. class Sales extends Employee {
17. // inse
8、rt method here
18. }
Which two methods, inserted independently at line 17, correctly
complete the Sales class? (Choose two.)
A. double getSalesAmount() { return 1230.45; }
B. public double getSalesAmount() { return 1230.45; }
C. private double getSalesAmount() { return 1230.45; }
D. protected
9、 double getSalesAmount() { return 1230.45; }
答案：AB
考點(diǎn)：抽象類(lèi)被繼承時(shí)，方法的可見(jiàn)度問(wèn)題。
說(shuō)明：當(dāng)抽象類(lèi)被繼承時(shí)，子類(lèi)必須重寫(xiě)父類(lèi)的抽象方法，且子類(lèi)的方法可見(jiàn)度必須比父類(lèi)的可見(jiàn)度更廣。
Question 5
Given:
10. interface Data { public void load(); }
11. abstract class Info { public abstract void load(); }
Which class correctly uses the Data interface and In
10、fo class?
A. public class Employee extends Info implements Data {
public void load() { /*do something*/ }
}
B. public class Employee implements Info extends Data {
public void load() { /*do something*/ }
}
C. public class Employee extends Info implements Data {
public void load() { /*do some
11、thing */ }
public void Info.load() { /*do something*/ }
}
D. public class Employee implements Info extends Data {
public void Data.load() { /*d something */ }
public void load() { /*do something */ }
}
E. public class Employee implements Info extends Data {
public void load() { /*do somethin
12、g */ }
public void Info.load(){ /*do something*/ }
}
F. public class Employee extends Info implements Data{
public void Data.load() { /*do something*/ }
public void Info.load() { /*do something*/ }
}
答案：A
考點(diǎn)：抽象類(lèi)和接口在繼承和繼承接口中的問(wèn)題。
說(shuō)明：子類(lèi)可以同時(shí)繼承抽象類(lèi)和接口類(lèi)，子類(lèi)的必須必須重寫(xiě)抽象類(lèi)和接口的方法。如果抽象類(lèi)和接口有相同的未完成的方法名，這子類(lèi)中只
13、要寫(xiě)一個(gè)就可以。
Question 6
Given:
11. public abstract class Shape {
12. private int x;
13. private int y;
14. public abstract void draw();
15. public void setAnchor(int x, int y) {
16. this.x = x;
17. this.y = y;
18. }
19. }
Which two classes use the Shape class correctly? (Choose two.)
A. p
14、ublic class Circle implements Shape {
private int radius;
}
B. public abstract class Circle extends Shape {
private int radius;
}
C. public class Circle extends Shape {
private int radius;
public void draw();
}
D. public abstract class Circle implements Shape {
private int radius;
public
15、 void draw();
}
E. public class Circle extends Shape {
private int radius;
public void draw() {/* code here */}
}
F. public abstract class Circle implements Shape {
private int radius;
public void draw() { / code here */ }
}
答案：E
考點(diǎn)：繼承環(huán)境下，抽象類(lèi)的抽象放法被繼承時(shí)的問(wèn)題.
說(shuō)明：抽象類(lèi)被繼承時(shí)應(yīng)使用extends，且抽象類(lèi)中的抽象方法應(yīng)
16、給在子類(lèi)中完成。
Question 7
Which two classes correctly implement both the java.lang.Runnable
and the java.lang.Clonable interfaces? (Choose two.)
A. public class Session
implements Runnable, Clonable {
public void run();
public Object clone();
}
B. public class Session
extends Runnable, Clon
17、able {
public void run() { / do something */ }
public Object clone() { / make a copy */ }
}
C. public class Session
implements Runnable, Clonable {
public void run() { / do something */ }
public Object clone() { /* make a copy */ }
}
D. public abstract class Session
implements Runnable, Cl
18、onable {
public void run() { / do something */ }
public Object clone() { /*make a copy */ }
}
E. public class Session
implements Runnable, implements Clonable {
public void run() { / do something */ }
public Object clone() { / make a copy */ }
}
答案：CE
考點(diǎn)：考察接口被子類(lèi)繼承的規(guī)則。
說(shuō)明：接口被繼承時(shí)應(yīng)在類(lèi)后面寫(xiě)上被繼承的
19、接口，且要完成接口中所有未完成的方法。
Question 8
Click the Exhibit button.
1. public class GoTest {
2. public static void main(String[] args) {
3. Sente a = new Sente(); a.go();
4. Goban b = new Goban(); b.go();
5. Stone c = new Stone(); c.go();
6. }
7. }
8.
9. class Sente implements Go {
10. public vo
20、id go() { System.out.println(”go in Sente.”); }
11. }
12.
13. class Goban extends Sente {
14. public void go() { System.out.println(”go in Goban”); }
15. }
16.
17. class Stone extends Goban implements Go { }
18.
19. interface Go { public void go(); }
What is the result?
A. go in Goban
go
21、 in Sente
go in Sente
B. go in Sente
go in Sente
go in Goban
C. go in Sente
go in Goban
go in Goban
D. go in Goban
go in Goban
go in Sente
E. Compilation fails because of an error in line 17.
答案：C
考點(diǎn)：考察接口被實(shí)現(xiàn)和的問(wèn)題。
說(shuō)明：本題考察接口被實(shí)現(xiàn)時(shí)應(yīng)重寫(xiě)接口中的方法，當(dāng)一個(gè)子類(lèi)同時(shí)繼承和實(shí)現(xiàn)接口時(shí)，在兩父類(lèi)中都有的方法，在子類(lèi)中只需繼承非接口父類(lèi)的方法或重寫(xiě)父類(lèi)的方
22、法。
Question 9
Given:
11. public static void parse(String str) {
12. try {
13. float f= Float.parseFloat(str);
14. } catch (NumberFormatException nfe) {
15. f= 0;
16. } finally {
17. System.out.println(f);
18. }
19. }
20. public static void main(String[] args) {
21. parse(“invalid”);
23、
22. }
What is the result?
A. 0.0
B. Compilation fails.
C. A ParseException is thrown by the parse method at runtime.
D. A NumberFormatException is thrown by the parse method at
runtime.
答案：B
考點(diǎn)：考察異常和變量定義問(wèn)題。
說(shuō)明：本題通過(guò)異常來(lái)考察變量定義的使用塊，在try塊中定義的f不能在catch塊中不能再使用f，否則將導(dǎo)致編譯錯(cuò)誤。
Question 10
Click
24、 the Exhibit button.
1. public class Test {
2. int x= 12;
3. public void method(int x) {
4. x+=x;
5. System.out.println(x);
6. }
7. }
Given:
34. Test t = new Test();
35. t.method(5);
What is the output from line 5 of the Test class?
A. 5
B. 10
C. 12
D. 17
E. 24
答案：C
考點(diǎn)：考察形參與實(shí)參的用法。
25、
說(shuō)明：本題method（）方法被調(diào)用且把5賦值給形參后，在方法中只改變形參的值，不管形參如何改變，都不影響實(shí)參的值。
Question 11
Given:
55. int[] x= {1, 2,3,4, 5}; // new int[]{1,2,3,4,5}
56. int y[] =x;
57. System.out.println(y[2]);
Which is true?
A. Line 57 will print the value 2.
B. Line 57 will print the value 3.
C. Compilation will fail be
26、cause of an error in line 55.
D. Compilation will fail because of an error in line 56.
答案：B
考點(diǎn)：考察數(shù)組的用法。
說(shuō)明：本題數(shù)組x把值賦給數(shù)組y，再通過(guò)數(shù)組下標(biāo)來(lái)找數(shù)值。
Question 12
Given:
35. String #name = “Jane Doe”;
36. int $age=24;
37. Double _height = 123.5;
38. double ~temp = 37.5;
Which two are true? (Ch
27、oose two.)
A. Line 35 will not compile.
B. Line 36 will not compile.
C. Line 37 will not compile.
D. Line 38 will not compile.
答案：BC
考點(diǎn)：標(biāo)示符的用法。
說(shuō)明：標(biāo)識(shí)符由大小寫(xiě)字母,下劃線,數(shù)字,$符號(hào)組成，開(kāi)頭可以是大小寫(xiě)字母,下劃線,和$符號(hào)。
Question13
Which two code fragments correctly create and initialize a static array
of int element
28、s? (Choose two.)
A. static final int[] a = { 100,200 };
B. static final int[] a;
static { a=new int[2]; a[0]=100; a[1]=200; }
C. static final int[] a = new int[2] { 100,200 };
D. static final int[] a;
static void init() { a = new int[3]; a[0]=100; a[1]=200; }
答案：AC
考點(diǎn)：考察數(shù)組的定義。
說(shuō)明：一個(gè)數(shù)組可以直接初始
29、化，系統(tǒng)會(huì)制動(dòng)幫你創(chuàng)建，也可以創(chuàng)建后在初始化。
Question 14
Given:
11. public static void main(String[] args) {
12. Object obj =new int[] { 1,2,3 };
13. int[] someArray = (int[])obj;
14. for (int i: someArray) System.out.print(i +“ “)
15. }
‘What is the result?
A. 1 2 3
B. Compilation fails because of an err
30、or in line 12.
C. Compilation fails because of an error in line 13.
D. Compilation fails because of an error in line 14.
E. A ClassCastException is thrown at runtime.
答案：A
考點(diǎn)：考察數(shù)組的用法。
說(shuō)明：本題創(chuàng)建一個(gè)數(shù)組賦給它的引用變量為obj，在通過(guò)obj把數(shù)組的地址賦給array。
Question 15
Given:
10. class Foo {
11. static void alpha(
31、) { /* more code here */ }
12. void beta() { /* more code here */ }
13. }
Which two are true? (Choose two.)
A. Foo.beta() is a valid invocation of beta().
B. Foo.alpha() is a valid invocation of alpha().
C. Method beta() can directly call method alpha().
D. Method alpha() can directly call me
32、thod beta().
答案：
Question 16
A programmer needs to create a logging method that can accept an
arbitrary number of arguments. For example, it may be called in these
ways:
logIt(”log message 1 “);
logIt(”log message2”,”log message3”);
logIt(”log message4”, “l(fā)og message5”, “l(fā)og message6“);
33、
Which declaration satisfies this requirement?
A. public void logIt(String * msgs)
B. public void logIt(String [] msgs)
C. public void logIt(String... msgs)
D. public void logIt(String msg1, String msg2, String msg3)
Question 17
A programmer is designing a class to encapsulate the inf
34、ormation
about an inventory item. A JavaBeans component is needed to
do this. The Inventoryltem class has private instance variables to store
the item information:
10. private int itemId;
11. private String name;
12. private String description;
Which method signature follows the JavaBeans nam
35、ing standards for
modifying the itemld instance variable?
A. itemID(int itemId)
B. update(int itemId)
C. setItemId(int itemId)
D. mutateItemId(int itemId)
E. updateItemID(int itemId)
Question 18
Click the Exhibit button.
1. public class A {
2.
3. private int counter = 0;
4.
5. p
36、ublic static int getInstanceCount() {
6. return counter;
7. }
8.
9. public A() {
10. counter++;
11. }
12.
13. }
Given this code from Class B:
25. A a1 =new A();
26. A a2 =new A();
27. A a3 =new A();
28. System.out.printIn(A.getInstanceCount() );
What is the result?
A. Compilation of c
37、lass A fails.
B. Line 28 prints the value 3 to System.out.
C. Line 28 prints the value 1 to System.out.
D. A runtime error occurs when line 25 executes.
E. Compilation fails because of an error on line 28.
Question 19
A JavaBeans component has the following field:
11. private boolean ena
38、bled;
Which two pairs of method declarations follow the JavaBeans standard
for accessing this field? (Choose two.)
A. public void setEnabled( boolean enabled)
public boolean getEnabled()
B. public void setEnabled( boolean enabled)
public void isEnabled()
C. public void setEnabled( boolean e
39、nabled)
public boolean isEnabled()
D. public boolean setEnabled( boolean enabled)
public boolean getEnabled()
Question 20
41. Given:
10. class One {
11. public One foo() { return this; }
12. }
13. class Two extends One {
14. public One foo() { return this; }
15. }
16. class Three e
40、xtends Two {
17. // insert method here
18. }
Which two methods, inserted individually, correctly complete the Three
class? (Choose two.)
A. public void foo() { }
B. public int foo() { return 3; }
C. public Two foo() { return this; }
D. public One foo() { return this; }
E. public Object foo(
41、) { return this; }
Question 21
Given:
10. class One {
11. void foo() {}
12. }
13. class Two extends One {
14. //insert method here
15. }
Which three methods, inserted individually at line 14, will correctly
complete class Two? (Choose three.)
A. int foo() { /* more code here */ }
B.
42、void foo() { /* more code here */ }
C. public void foo() { /* more code here */ }
D. private void foo() { /* more code here */ }
E. protected void foo() { /* more code here */ }
Question 22
Click the Exhibit button.
1. public interface A {
2. public void doSomething(String thing);
3
43、. }
1. public class AImpl implements A {
2. public void doSomething(String msg) { }
3. }
1. public class B {
2. public A doit() {
3. // more code here
4. }
5.
6. public String execute() {
7. // more code here
8. }
9. }
1. public class C extends B {
2. public AImpl doit() {
3. // more
44、code here
4. }
5.
6. public Object execute() {
7. // more code here
8. }
9. }
Which statement is true about the classes and interfaces in the
exhibit?
A. Compilation will succeed for all classes and interfaces.
B. Compilation of class C will fail because of an error in line 2.
C. Compilation of class C will fail because of an error in line 6.
D. Compilation of class AImpl will fail because of an error in line 2.
JAVA基礎(chǔ)面試題1
