⑴ （java類和對象練習）.
importjava.util.Arrays;
importjava.util.Comparator;
classStudent
{
publicStringstuNo;
publicStringstuName;
publicintstuAge;
publicStudent(StringstuNo,StringstuName,intstuAge)
{
this.stuNo=stuNo;
this.stuName=stuName;
this.stuAge=stuAge;
}
publicvoidaddAge()
{
stuAge++;
}
publicStringtoString()
{
return"No:"+讓咐stuNo+"Name:"+stuName+"Age:"+stuAge;
}
}
<稿衫Student>
{
@Override
publicintcompare(Studento1,Studento2)
{
//TODOAuto-generatedmethodstub
returno1.stuNo.compareTo(o2.stuNo);
}
}
publicclassTest3
{
publicstaticvoidmain(String[]args)
{
Student[]students=newStudent[5];
students[0]=newStudent("1003","a",12);
students[1]=newStudent("1002","b",13);
students[2]=newStudent("1004","c",14);
students[3]=newStudent("1001","d",15);
students[4]鍵滑腔=newStudent("1005","e",16);
Arrays.sort(students,newStudentOrder());
intcount=0;
for(inti=0;i<5;i++)
{
System.out.println(students[i]);
students[i].addAge();
if(students[i].stuAge>20)
count++;
}
System.out.println("大於20歲的人數:"+count);
}
}
⑵ JAVA程序題~關於類和對象
所謂對象就是真實世界中的實體唯辯鬧，對象與實體是一一對應的，也就是說現實灶頌世界中每一個實體都是一個對象，它是一種具體的概念。類是具備某些共同特徵指罩的實體的集合，它是一種抽象的概念，用程序設計的語言來說，類是一種抽象的數據類型，它是對所具有相同特徵實體的抽象。
⑶ 用JAVA編程 類與對象的基礎題
class Phone{
private String phonenumber;
public void setPhonenumber(String phonenumber){
this.phonenumber=phonenumber;
}
public String getPhonenumber(){
return phonenumber;
}
public void recCall(){
System.out.println("接到一個電話");
}
public void telCall(){
System.out.println("撥出一個電話");
}
}class Fixedphone extends Phone{
private String phonenumber;//號碼是私有，設置為private，不可繼承
public void recCall(){
System.out.println("以"+this.phonenumber+"呼出了一個電話"); //重載了父類的recCall
}
}class Cordlessphone extends Fixedphone{
private String phonenumber;
public void info(){
System.out.println("這是無繩電話的信息");
}
}interface Moveable{
public void moveinfo();
}class Mobilephone extends Phone implements Moveable{
private String phonenumber;
public void moveinfo(){
System.out.println("我實現了可移動性");
}
}public class PhoneTest{
public static void main(String a[]){
Phone[] p=new Phone[5];
Phone p1=new Phone();
p1.setPhonenumber("123456789");
p[0]=p1;
Phone p2=new Phone();
p2.setPhonenumber("987654321");
p[1]=p2;
Mobilephone mp=new Mobilephone();
mp.setPhonenumber("11111");
p[2]=mp;
Fixedphone fp=new Fixedphone();
fp.setPhonenumber("22222");
p[3]=fp;
Cordlessphone cp=new Cordlessphone();
cp.setPhonenumber("33333");
p[4]=cp;
for(int i=0;i<p.length;i++){
System.out.println(p[i].getPhonenumber());
} p[4]=p[1];
System.out.println(p[4].getPhonenumber());
}} 寫的不是很好，希望對你有幫助噶
⑷ 關於java的問題:類與對象
類是一組數據和函數的集合，只是抽象的概念，它的作用就是生成對象，它生成對象後，就為模答橡這個對象分了一塊存儲區，類可以生成無限多個對象，每個對象都有自己的存儲區，在類里定義的數據和函數在這個對象里都有了
類生成的不同對象都有自己不同的存儲區，所以每個對象的數據和函數都存在不同的地方，改變了這個對象的數據不會印象另一個對象的數據，但是加了static後，舉猛數旦旁據和函數就是靜態的了，靜態的數據或函數存在一個存儲區，因為是存在一個地方，所以所有對象對這個數據是共有的，只要它一改變，所有對象的這個數據都會改變
⑸ 誰能提供JAVA 類和對象的練習題!!
Question No: 1
public class test (
2. public static void main (String args[]) {
3. int i = 0xFFFFFFF1;
4. int j = ~i;
5.
6. }
7. )
What is the decimal value of j at line 5?
A. 0
B. 1
C. 14
D. –15
E. An error at line 3 causes compilation to fail.
F. An error at line 4 causes compilation to fail.
答案: C
Question No: 2
Given:
Integer i = new Integer (42);
Long 1 = new Long (42);
Double d = new Double (42.0);
Which two expressions evaluate to True? (Choose Two)
A. (i ==1)
B. (i == d)
C. (d == 1)
D. (i.equals (d))
E. (d.equals (i))
F. (i.equals (42))
答案: D, E
Question No: 3
Exhibit :
1. public class test (
2. private static int j = 0;
3.
4. private static boolean methodB(int k) (
5. j += k;
6. return true;
6. )
7.
8. public static void methodA(int i) {
9. boolean b:
10. b = i < 10 | methodB (4);
11. b = i < 10 || methodB (8);
12. }
13.
14. public static void main (String args[] ) (
15. methodA (0);
16. system.out.printIn(j);
17. )
18. )
What is the result?
A. The program prints 「0」
B. The program prints 「4」
C. The program prints 「8」
D. The program prints 「12」
E. The code does not complete.
答案: B
Question No: 4
Given
1. Public class test (
2. Public static void main (String args[]) (
3. System.out.printIn (6 ^ 3);
4. )
5. )
What is the output?
答案: 5
Question No: 5
Given:
1. public class Foo {
2. public static void main (String [] args) {
3. StringBuffer a = new StringBuffer (「A」);
4. StringBuffer b = new StringBuffer (「B」);
5. operate (a,b);
6. system.out.printIn{a + 「,」 +b};
7. }
8. static void operate (StringBuffer x, StringBuffer y) {
9. x.append {y};
10. y = x;
11. }
12. }
What is the result?
A. The code compiles and prints 「A,B」.
B. The code compiles and prints 「A,A」.
C. The code compiles and prints 「B,B」.
D. The code compiles and prints 「AB,B」.
E. The code compiles and prints 「AB,AB」.
F. The code does not compile because 「+」 cannot be overloaded for StringBuffer.
答案: D
Question No: 6
Exhibit:
1. Public class test (
2. Public static void stringReplace (String text) (
3. Text = text.replace (『j』 , 『i』);
4. )
5.
6. public static void bufferReplace (StringBuffer text) (
7. text = text.append (「C」)
8. )
9.
10. public static void main (String args[]) (
11. String textString = new String (「java」);
12. StringBuffer text BufferString = new StringBuffer (「java」);
13.
14. stringReplace (textString);
15. BufferReplace (textBuffer);
16.
17. System.out.printIn (textString + textBuffer);
18. )
19. )
What is the output?
答案: JAVAJAVA
Question No: 7
Exhibit:
1. public class test {
2. public static void add3 (Integer i) }
3. int val = i.intValue ( );
4. val += 3;
5. i = new Integer (val);
6. )
7.
8. public static void main (String args [ ] ) {
9. Integer i = new Integer (0);
10. add3 (i);
11. system.out.printIn (i.intValue ( ) );
12. }
13. )
What is the result?
A. Compilation will fail.
B. The program prints 「0」.
C. The program prints 「3」.
D. Compilation will succeed but an exception will be thrown at line 3.
答案: B
Question No: 8
Given:
1. public class ConstOver {
2. public ConstOver (int x, int y, int z) {
3. }
4. }
Which two overload the ConstOver constructor? (Choose Two)
A. ConstOver ( ) { }
B. Protected int ConstOver ( ) { }
C. Private ConstOver (int z, int y, byte x) { }
D. Public Object ConstOver (int x, int y, int z) { }
E. Public void ConstOver (byte x, byte y, byte z) { }
答案: A, C
Question No: 9
Given:
1. public class MethodOver {
2. public void setVar (int a, int b, float c) {
3. }
4. }
Which two overload the setVar method? (Choose Two)
A. Private void setVar (int a, float c, int b) { }
B. Protected void setVar (int a, int b, float c) { }
C. Public int setVar (int a, float c, int b) (return a;)
D. Public int setVar (int a, int b, float c) (return a;)
E. Protected float setVar (int a, int b, float c) (return c;)
答案: A, C
Question No: 10
Given:
1. class BaseClass {
2. Private float x = 1.0f ;
3. protected float getVar ( ) ( return x;)
4. }
5. class Subclass extends BaseClass (
6. private float x = 2.0f;
7. //insert code here
8. )
Which two are valid examples of method overriding? (Choose Two)
A. Float getVar ( ) { return x;}
B. Public float getVar ( ) { return x;}
C. Float double getVar ( ) { return x;}
D. Public float getVar ( ) { return x;}
E. Public float getVar (float f ) { return f;}
答案: B, D
Question No: 11
Which two demonstrate an 「is a」 relationship? (Choose Two)
A. public interface Person { }
public class Employee extends Person { }
B. public interface Shape { }
public class Employee extends Shape { }
C. public interface Color { }
public class Employee extends Color { }
D. public class Species { }
public class Animal (private Species species;)
E. interface Component { }
Class Container implements Component (
Private Component[ ] children;
)
答案: D, E
Question No: 12
Which statement is true?
A. An anonymous inner class may be declared as final.
B. An anonymous inner class can be declared as private.
C. An anonymous inner class can implement multiple interfaces.
D. An anonymous inner class can access final variables in any enclosing scope.
E. Construction of an instance of a static inner class requires an instance of the enclosing outer class.
答案: D
Question No 13
Given:
1. package foo;
2.
3. public class Outer (
4. public static class Inner (
5. )
6. )
Which statement is true?
A. An instance of the Inner class can be constructed with 「new Outer.Inner ()」
B. An instance of the inner class cannot be constructed outside of package foo.
C. An instance of the inner class can only be constructed from within the outer class.
D. From within the package bar, an instance of the inner class can be constructed with 「new inner()」
答案: A
Question No 14
Exhibit:
1. public class enclosingone (
2. public class insideone{}
3. )
4. public class inertest(
5. public static void main (string[]args)(
6. enclosingone eo= new enclosingone ();
7. //insert code here
8. )
9. )
Which statement at line 7 constructs an instance of the inner class?
A. InsideOnew ei= eo.new InsideOn();
B. Eo.InsideOne ei = eo.new InsideOne();
C. InsideOne ei = EnclosingOne.new InsideOne();
D. EnclosingOne.InsideOne ei = eo.new InsideOne();
答案: D
Question No 15
Exhibit:
1. interface foo {
2. int k = 0;
3. }
4.
5. public class test implements Foo (
6. public static void main(String args[]) (
7. int i;
8. Test test = new test ();
9. i= test.k;
10.i= Test.k;
11.i= Foo.k;
12.)
13.)
14.
What is the result?
A. Compilation succeeds.
B. An error at line 2 causes compilation to fail.
C. An error at line 9 causes compilation to fail.
D. An error at line 10 causes compilation to fail.
E. An error at line 11 causes compilation to fail.
答案: A
Question No 16
Given:
1. //point X
2. public class foo (
3. public static void main (String[]args) throws Exception {
4. printWriter out = new PrintWriter (new
5. java.io.outputStreamWriter (System.out), true;
6. out.printIn(「Hello」);
7. )
8. }
Which statement at PointX on line 1 allows this code to compile and run?
A. Import java.io.PrintWriter;
B. Include java.io.PrintWriter;
C. Import java.io.OutputStreamWriter;
D. Include java.io.OutputStreamWriter;
E. No statement is needed.
答案: A
Question No 17
Which two statements are reserved words in Java? (Choose Two)
A. Run
B. Import
C. Default
D. Implement
答案: B, C
Question No 18
Which three are valid declarations of a float? (Choose Three)
A. Float foo = -1;
B. Float foo = 1.0;
C. Float foo = 42e1;
D. Float foo = 2.02f;
E. Float foo = 3.03d;
F. Float foo = 0x0123;
答案: A, D, F
Question No 19
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Question No 19
Given:
8. int index = 1;
9. boolean[] test = new Boolean[3];
10. boolean foo= test [index];
What is the result?
A. Foo has the value of 0.
B. Foo has the value of null.
C. Foo has the value of true.
D. Foo has the value of false.
E. An exception is thrown.
F. The code will not compile.
答案: D
Question No 20
Given:
1. public class test(
2. public static void main(string[]args){
3. string foo = args [1];
4. string foo = args [2];
5. string foo = args [3];
6. }
7. )
And command line invocation:
Java Test red green blue
What is the result?
A. Baz has the value of 「」
B. Baz has the value of null
C. Baz has the value of 「red」
D. Baz has the value of 「blue」
E. Bax has the value of 「green」
F. The code does not compile.
G. The program throws an exception.
答案: G
Question No 21
Given:
8. int index = 1;
9. int [] foo = new int [3];
10.int bar = foo [index];
11.int baz = bar + index;
What is the result?
A. Baz has the value of 0
B. Baz has the value of 1
C. Baz has the value of 2
D. An exception is thrown.
E. The code will not compile.
答案: B
Question No 22
Given:
1. public class foo {
2. public static void main (String[]args) {
3. String s;
4. system.out.printIn (「s=」 + s);
5. }
6. }
What is the result?
A. The code compiles and 「s=」 is printed.
B. The code compiles and 「s=null」 is printed.
C. The code does not compile because string s is not initialized.
D. The code does not compile because string s cannot be referenced.
E. The code compiles, but a NullPointerException is thrown when toString is called.
答案: C
Question No 23
Which will declare a method that forces a subclass to implement it?
A. Public double methoda();
B. Static void methoda (double d1) {}
C. Public native double methoda();
D. Abstract public void methoda();
E. Protected void methoda (double d1){}
答案: D
Question No 24
You want subclasses in any package to have access to members of a superclass. Which is the most
restrictive access modifier that will accomplish this objective?
A. Public
B. Private
C. Protected
D. Transient
E. No access modifier is qualified
答案: C
Question No 25
Given:
1. abstract class abstrctIt {
2. abstract float getFloat ();
3. }
4. public class AbstractTest extends AbstractIt {
5. private float f1= 1.0f;
6. private float getFloat () {return f1;}
7. }
What is the result?
A. Compilation is successful.
B. An error on line 6 causes a runtime failure.
C. An error at line 6 causes compilation to fail.
D. An error at line 2 causes compilation to fail.
答案: C
Question No 26
Exhibit:
1. public class test(
2. public int aMethod()[
3. static int i=0;
4. i++;
5. return I;
6. ]
7. public static void main (String args[]){
8. test test = new test();
9. test.aMethod();
10.int j = test.aMethod();
11.System.out.printIn(j);
12.}
13.)
What is the result?
A. Compilation will fail.
B. Compilation will succeed and the program will print 「0」
C. Compilation will succeed and the program will print 「1」
D. Compilation will succeed and the program will print 「2」
答案: D
Question No 27
Given:
1. class super {
2. public float getNum() {return 3.0f;}
3. }
4.
5. public class Sub extends Super {
6.
7. }
Which method, placed at line 6, will cause a compiler error?
A. Public float getNum() {return 4.0f; }
B. Public void getNum () { }
C. Public void getNum (double d) { }
D. Public double getNum (float d) {retrun 4.0f; }
答案: B
Question No 28
Which declaration prevents creating a subclass of an outer class?
A. Static class FooBar{}
B. Private class FooBar{}
C. Abstract public class FooBar{}
D. Final public class FooBar{}
E. Final abstract class FooBar{}
答案: D
Question No 29
Given:
1. byte [] arry1, array2[];
2. byte array3 [][];
3. byte[][] array4;
If each array has been initialized, which statement will cause a compiler error?
A. Array2 = array1;
B. Array2 = array3;
C. Array2 = array4;
D. Both A and B
E. Both A and C
F. Both B and C
答案: F
Question No 30
Exhibit:
1. class super (
2. public int I = 0;
3.
4. public super (string text) (
5. I = 1
6. )
7. )
8.
9. public class sub extends super (
10. public sub (string text) (
11. i= 2
12. )
13.
14. public static void main (straing args[]) (
15. sub sub = new sub (「Hello」);
16. system.out. PrintIn(sub.i);
17. )
18. )
What is the result?
A. Compilation will fail.
B. Compilation will succeed and the program will print 「0」
C. Compilation will succeed and the program will print 「1」
D. Compilation will succeed and the program will print 「2」
答案: A
Question No 31
Given:
1. public class returnIt (
2. returnType methodA(byte x, double y) (
3. return (short) x/y * 2;
4. )
5. )
What is the valid returnType for methodA in line 2?
A. Int
B. Byte
C. Long
D. Short
E. Float
F. Double
答案: F
Question No 32
Given the ActionEvent, which method allows you to identify the affected component?
A. GetClass.
B. GetTarget.
C. GetSource.
D. GetComponent.
E. GetTargetComponent.
答案: C
Question No 33
Which is a method of the MouseMotionListener interface?
A. Public void mouseMoved(MouseEvent)
B. Public boolean mouseMoved(MouseEvent)
C. Public void mouseMoved(MouseMotionEvent)
D. Public boolean MouseMoved(MouseMotionEvent)
E. Public boolean mouseMoved(MouseMotionEvent)
答案: A
⑹ 在Java中,以下關於類與對象描述錯誤的是().（選擇二項）
b和c錯誤，選bc，b和c反了，應該是類是對象的一種抽象，對象是類的一個實例