public class Test1 { public static int indexOf(char[] array,char c) throws IllegalArgumentException { if (array == null || array.length <=0 ) throw new IllegalArgumentException("Array is null"); for (int i = 0; i<array.length; i++) if (array[i] == c) return i; return -1; } public static void main(String args[]) { try { char[] a = {'a','b'}; char[] b = null; System.out.println(indexOf(a,'b')); System.out.println(indexOf(a,'c')); System.out.println(indexOf(b,'a')); } catch (IllegalArgumentException e) {System.out.println(e.getMessage());} finally { try { char[] c = {}; System.out.println(indexOf(c,'a')); } catch (IllegalArgumentException e) {System.out.println(e.getMessage());} } } }
public class Test2 { public static void main(String args[]) { int[] a = {1,2,3}; StringBuilder s = new StringBuilder(); for (int i = 0; i < a.length; i++) { s.append(a[i]); if (i < a.length - 1) s.append(','); } System.out.println(s); } }
import java.io.*;public class Test3 { BufferedReader br; public Test3(String file) { try { br = new BufferedReader(new FileReader(file)); } catch (FileNotFoundException e) { e.printStackTrace(); } }
public String readLine() { StringBuilder s = new StringBuilder(); String line; try { for (int i = 1;(line = br.readLine()) != null; i++) s.append(i).append(':').append(line).append('\n'); } catch (IOException e) { e.printStackTrace(); } return s.toString(); }
public static void main(String args[]) { Test3 t = new Test3("Test1.java"); System.out.print(t.readLine()); } }
第5题...不如调用oracle的exp命令来备份就算了......
import java.io.*;public class Test4 { public static void main(String args[]) { try { BufferedReader br = new BufferedReader(new FileReader("test.txt")); String line; StringBuilder result = new StringBuilder();
while ((line = br.readLine()) != null) { int pos1 = line.indexOf(' '); int pos2 = line.indexOf(' ', pos1 + 1);
if (pos1 == -1) { result.append(line).append('\n'); continue; } result.append(line.substring(0, pos1)).append(',');
public static int search(char a[],char b) {
if(a==null)
throw new IllegalArgumentException();
String temp=new String(a);
return temp.indexOf(b);
}
编写一个程序,这个程序把一个整数数组中的每个元素用逗号连接成一个字符串,例如,根据内容为[1][2][3]的数组形成内容为"1,2,3"的字符串。
public static String append(char a[])
{
StringBuffer sb=new StringBuffer();
for(int i=0;i<a.length;i++)
{
if(i!=0) sb.append(",");
sb.append(a[i]);
}
return sb.toString();
}
请编写一个字符输入流的包装类,通过这个包装类对底层字符输入流进行包装,让程序通过这个包装类读取某个文本文件(例如,一个java源文件)时,能够在读取的每行前面都加上有行号和冒号。
import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;/**
*
* @author hongrui xing
*/
public class LineNumberReader extends BufferedReader{
private int lineNumber = 0;
public LineNumberReader(Reader in) {
super(in);
}
public String readLine() throws IOException {
StringBuffer sb= new StringBuffer();
synchronized (lock) {
String l = super.readLine();
if (l != null) {
lineNumber++;
sb.append(String.valueOf(lineNumber));
sb.append(":");
sb.append(l);
}
return sb.toString();
}
}
}在javascript视频的第七讲的第一个片断,也就是网站上提供的免费片断《正则表达式的应用》中,讲到了将一个保存有ip地址与地区对照关系的文本文件导入到数据库时,应该将其中的某些空格替换成逗号(,),即对于如下格式的文本文件内容:
起始IP 结束IP 地区
---------------------------------------------------------------
61.54.231.245 61.54.231.245 河南省安阳市 新世纪网吧
61.54.231.246 61.54.231.246 河南省安阳市 未知地区
61.54.231.9 61.54.231.247 河南省安阳市 红日网吧
61.54.231.248 61.54.231.248 河南省安阳市 安阳师范学院
61.54.231.249 61.54.231.249 河南省安阳市 黑蜘蛛网吧(师范学院附近)
应转换成下面的这种格式:
61.54.231.245,61.54.231.245,河南省安阳市 新世纪网吧
61.54.231.246,61.54.231.246,河南省安阳市 未知地区
61.54.231.247,61.54.231.247,河南省安阳市 红日网吧
61.54.231.248,61.54.231.248,河南省安阳市 安阳师范学院
61.54.231.249,61.54.231.249,河南省安阳市 黑蜘蛛网吧(师范学院附近)
代码
String a="61.54.231.245 61.54.231.245 河南省安阳市 新世纪网吧 ";
String regex = "(((2[0-4]\\d)|(25[0-5]))|(1\\d{2})|([1-9]\\d)|(\\d))[.](((2[0-4]\\d)|(25[0-5]))|(1\\d{2})|([1-9]\\d)|(\\d))[.](((2[0-4]\\d)|(25[0-5]))|(1\\d{2})|([1-9]\\d)|(\\d))[.](((2[0-4]\\d)|(25[0-5]))|(1\\d{2})|([1-9]\\d)|(\\d)\\s)";
a=a.replaceAll(regex,"$0,");
System.out.println(a);
public static int search(char a[],char b) {
if(a==null)
throw new IllegalArgumentException();
String temp=new String(a);
if(!(temp.indexOf(b)>=0)){
return -1;
}
else
return temp.indexOf(b);
}增加了字符在数组中不存在字符返回-1。hongrui的回复那里少了这个
public static int indexOf(char[] array,char c) throws IllegalArgumentException {
if (array == null || array.length <=0 )
throw new IllegalArgumentException("Array is null");
for (int i = 0; i<array.length; i++)
if (array[i] == c)
return i;
return -1;
}
public static void main(String args[]) {
try {
char[] a = {'a','b'};
char[] b = null;
System.out.println(indexOf(a,'b'));
System.out.println(indexOf(a,'c'));
System.out.println(indexOf(b,'a'));
} catch (IllegalArgumentException e) {System.out.println(e.getMessage());}
finally {
try {
char[] c = {};
System.out.println(indexOf(c,'a'));
} catch (IllegalArgumentException e) {System.out.println(e.getMessage());}
}
}
}
public static void main(String args[]) {
int[] a = {1,2,3};
StringBuilder s = new StringBuilder();
for (int i = 0; i < a.length; i++) {
s.append(a[i]);
if (i < a.length - 1)
s.append(',');
}
System.out.println(s);
}
}
BufferedReader br; public Test3(String file) {
try {
br = new BufferedReader(new FileReader(file));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
public String readLine() {
StringBuilder s = new StringBuilder();
String line;
try {
for (int i = 1;(line = br.readLine()) != null; i++)
s.append(i).append(':').append(line).append('\n');
} catch (IOException e) {
e.printStackTrace();
}
return s.toString();
}
public static void main(String args[]) {
Test3 t = new Test3("Test1.java");
System.out.print(t.readLine());
}
}
public static void main(String args[]) {
try {
BufferedReader br = new BufferedReader(new FileReader("test.txt"));
String line;
StringBuilder result = new StringBuilder();
while ((line = br.readLine()) != null) {
int pos1 = line.indexOf(' ');
int pos2 = line.indexOf(' ', pos1 + 1);
if (pos1 == -1) {
result.append(line).append('\n');
continue;
}
result.append(line.substring(0, pos1)).append(',');
if (pos2 == -1)
result.append(pos1 + 1).append('\n');
else {
result.append(line.substring(pos1 + 1, pos2)).append(',');
result.append(line.substring(pos2 + 1)).append('\n');
}
}
System.out.print(result);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}