public class FatherClass {
public FatherClass() {
System.out.println(“FatherClass Create”); } } 子类:
package test;
import test.FatherClass;
public class ChildClass extends FatherClass {
public ChildClass() {
System.out.println(“ChildClass Create”); }
public static void main(String[] args) {
FatherClass fc = new FatherClass(); ChildClass cc = new ChildClass(); } }
输出结果：
C:>java test.ChildClass FatherClass Create FatherClass Create ChildClass Create
4、内部类的实现方式? 答：示例代码如下： package test;
public class OuterClass {
private class InterClass {
public InterClass() {
System.out.println(“InterClass Create”); } }
public OuterClass() {
InterClass ic = new InterClass();
System.out.println(“OuterClass Create”); }
public static void main(String[] args) {
OuterClass oc = new OuterClass();
} }
输出结果:
C:>java test/OuterClass InterClass Create OuterClass Create 再一个例题：
public class OuterClass {
private double d1 = 1.0; //insert code here }
You need to insert an inner class declaration at line 3. Which two inner class declarations are valid?(Choose two.) A. class InnerOne{
public static double methoda() {return d1;} }
B. public class InnerOne {
static double methoda() {return d1;} }
C. private class InnerOne{ double methoda() {return d1;} }
D. static class InnerOne {
protected double methoda() {return d1;} }
E. abstract class InnerOne{
public abstract double methoda(); }
说明如下：
一.静态内部类可以有静态成员，而非静态内部类则不能有静态成员。 故A、B错
二.静态内部类的非静态成员可以访问外部类的静态变量，而不可访问外部类的非静态变量；return d1出错。 故D错
三.非静态内部类的非静态成员可以访问外部类的非静态变量。 故C正确 四.答案为C、E
5、Java的通信编程，编程题(或问答)，用JAVA SOCKET编程，读服务器几个字符，再写入本地显示？ 答:Server端程序: package test; import java.net.*; import java.io.*; public class Server {
private ServerSocket ss;
private Socket socket; private BufferedReader in; private PrintWriter out; public Server() { try {
ss=new ServerSocket(10000); while(true) {
socket = ss.accept();
String RemoteIP = socket.getInetAddress().getHostAddress(); String RemotePort = “:”+socket.getLocalPort();
System.out.println(“A client come in!IP:”+RemoteIP+RemotePort); in = new BufferedReader(new
InputStreamReader(socket.getInputStream())); String line = in.readLine();
System.out.println(“Cleint send is :” + line);
out = new PrintWriter(socket.getOutputStream(),true); out.println(“Your Message Received!”); out.close(); in.close(); socket.close(); }
}catch (IOException e) {
out.println(“wrong”); } }
public static void main(String[] args) {
new Server(); } };
Client端程序: package test; import java.io.*; import java.net.*; public class Client {
Socket socket; BufferedReader in; PrintWriter out; public Client() { try {
System.out.println(“Try to Connect to 127.0.0.1:10000”); socket = new Socket(“127.0.0.1”,10000); System.out.println(“The Server Connected!”);
System.out.println(“Please enter some Character:”); BufferedReader line = new BufferedReader(new InputStreamReader(System.in));
out = new PrintWriter(socket.getOutputStream(),true); out.println(line.readLine());
in = new BufferedReader(new InputStreamReader(socket.getInputStream())); System.out.println(in.readLine()); out.close(); in.close(); socket.close();
}catch(IOException e) {
out.println(“Wrong”); } }
public static void main(String[] args) {
new Client(); } };
6、用JAVA实现一种排序，JAVA类实现序列化的方法(二种)？ 如在COLLECTION框架中，实现比较要实现什么样的接口？
答:用插入法进行排序代码如下 package test; import java.util.*; class InsertSort {
ArrayList al;
public InsertSort(int num,int mod) {
al = new ArrayList(num);
Random rand = new Random();
System.out.println(\ for (int i=0;i al.add(new Integer(Math.abs(rand.nextInt()) % mod + 1)); System.out.println(\ } } public void SortIt() { Integer tempInt; int MaxSize=1; for(int i=1;i { tempInt = (Integer)al.remove(i); if(tempInt.intValue()>=((Integer)al.get(MaxSize-1)).intValue()) { al.add(MaxSize,tempInt); MaxSize++; System.out.println(al.toString()); } else { for (int j=0;j (((Integer)al.get(j)).intValue()>=tempInt.intValue()) { al.add(j,tempInt); MaxSize++; System.out.println(al.toString()); break; } } } } System.out.println(\ for(int i=0;i System.out.println(\ } } public static void main(String[] args) { InsertSort is = new InsertSort(10,100); is.SortIt(); } } JAVA类实现序例化的方法是实现java.io.Serializable接口 Collection框架中实现比较要实现Comparable 接口和 Comparator 接口 7、编程：编写一个截取字符串的函数，输入为一个字符串和字节数，输出为按字节截取的字符串。 但是要保证汉字不被截半个，如“我ABC”4，应该截为“我AB”，输入“我ABC汉DEF”，6，应该输出为“我ABC”而不是“我ABC+汉的半个”。 答：代码如下: package test; class SplitString { String SplitStr; int SplitByte; public SplitString(String str,int bytes) { SplitStr=str;