Java——第六章（异常处理和文件IO流操作）—项目案例

1.. x:/a/b/c  创建一个文件 1.doc， 键盘输入两个字符串， 写入1.doc中， 两字符串在文件中是两行，    

你从1.doc中全部读出来，把每一个字符串都颠倒  写入2.doc中， 从2.doc  在读出来打印。

代码：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Scanner;

public class Demo05 {
public static final String path = "G:/a/b/c";
public static final String path1 = "G:/a/b/c/1.doc";
public static final String path2 = "G:/a/b/c/2.doc";

public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
Scanner sc = new Scanner(System.in);
System.out.println("输入两个字符串");
String str = sc.next();
String str1 = sc.next();
CreatDir(path);
String contant = str + "\r\n" + str1;
FileOutputStream fos = new FileOutputStream(path1);
Write(fos, contant);

FileInputStream fis = new FileInputStream(path1);
String contant1 = Read(fis);

String[] ss = contant1.split("\n");
String line1 = ss[0];
String line2 = ss[1];
System.out.println("第一个字符串： " + line1);
System.out.println("第二个字符串： " + line2);
System.out.println("第一个字符串颠倒后： " + DianDao(line1));
System.out.println("第二个字符串颠倒后： " + DianDao(line2));

FileOutputStream fos1 = new FileOutputStream(path2,true);
String ss1 = line1+"\r\n"+line2;
Write(fos1, ss1);

}

public static String Read(FileInputStream fis) throws IOException {
byte[] b = new byte[1024];
int len;
String contant1 = "";
while ((len = fis.read(b)) != -1) {
contant1 += new String(b, 0, len);
}
System.out.println(contant1);
return contant1;
}

public static void CreatDir(String path) {
new File(path).mkdirs();
}

public static void CreatFile(String path) {
try {
new File(path).createNewFile();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

public static void Write(FileOutputStream fos, String contant) {

try {
fos.write(contant.getBytes());
fos.flush();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
try {
fos.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}

public static String DianDao(String str) {
char[] c = str.toCharArray();
for (int i = 0; i < c.length / 2; i++) {
char temp = c[i];
c[i] = c[c.length - 1 - i];
c[c.length - 1 - i] = temp;
}
return new String(c);

}

}

同样可以用字符流做。

代码：

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;

public class Demo09 {
public static final String path="G:/a/b/c";
public static final String path1="G:/a/b/c/1.doc";
public static final String path2="G:/a/b/c/2.doc";
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
CreatDir(path);
CreatFile(path1);

Scanner sc = new Scanner(System.in);
String str = sc.next();
String str1=sc.next();
String contant = str+"\r\n"+str1+"\r\n";
FileWriter fw = new FileWriter(path1,true);
Write(fw, contant);
fw.close();

FileReader fr = new FileReader(path1);
String s =Read(fr);

String []ss =s.split("\n");
String line1 = ss[0];
String line2 = ss[1];

FileWriter fw1 = new FileWriter(path2,true);

Write(fw1, DiaoDao(line1));
Write(fw1, DiaoDao(line2));

fw1.close();

FileReader fr1 = new FileReader(path2);
Read(fr1);

}
/*
* 创建目录
*/
public static void CreatDir(String path)
{
new File(path).mkdirs();
}
//创建文件
public static void CreatFile(String path)
{
try {
new File(path).createNewFile();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//写方法
public static void Write(FileWriter fw,String contant)
{
try {
fw.write(contant);
fw.flush();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
//读方法
public static String Read(FileReader fr) throws Exception
{
char c[]= new char[1024];
int len;
String ss="";
while((len=fr.read(c))!=-1)
{
ss+=new String(c,0,len);
}
System.out.println(ss);
return ss;
}
//字符串颠倒
public static String DiaoDao(String str){
char[] c=str.toCharArray();
for (int i = 0; i < c.length/2; i++) {
char temp = c[i];
c[i]=c[c.length-1-i];
c[c.length-1-i]=temp;
}
return new String(c);
}

}

2..编写一个程序，其功能是将两个文件的内容合并到一个文件中。

代码：

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.Random;

public class Demo16 {

public static void main(String[] args) throws Exception{
// TODO Auto-generated method stub

/*
* 编写一个程序，其功能是将两个文件的内容合并到一个文件中。
*/
File fromfile = new File("G:/a/b/c/1.doc");
File tofile = new File("G:/a/b/c/2.doc");
FileReader fr = new FileReader(fromfile);
FileWriter fw = new FileWriter(tofile,true);
BufferedReader br = new BufferedReader(fr);
BufferedWriter bw = new BufferedWriter(fw);

String s ="";
while((s=br.readLine())!=null)
{
bw.write(s);
bw.flush();
fw.flush();

}
br.close();
fr.close();
bw.close();
fw.close();
}
}

3..编写一个程序实现以下功能：

①产生5000个1～9999之间的随机整数，将其存入文本文件a.txt中。

②从文件中读取这5000个整数，并计算其
c3e4
最大值、最小值和平均值并输出结果。

代码：

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.Random;

public class Demo17 {

public static void main(String[] args) throws Exception {

/*
* 编写一个程序实现以下功能：()考虑内存优化
①产生5000个1～9999之间的随机整数，将其存入文本文件a.txt中。
②从文件中读取这5000个整数，并计算其最大值、最小值和平均值并输出结果。
*/

Random r = new Random();
File file = new File("G:/a/b/c/a.txt");
FileWriter fw = new FileWriter(file);
BufferedWriter bw = new BufferedWriter(fw);

for (int i = 0; i < 5000; i++) {
bw.write((r.nextInt(9999)+1)+"");
bw.newLine();
bw.flush();
fw.flush();

}
bw.close();
fw.close();

FileReader fr = new FileReader(file);
BufferedReader br = new BufferedReader(fr);
String s="";
int index=0;
int a[] = new int [5000];
while((s=br.readLine())!=null)
{
System.out.println(s);
a[index] = Integer.valueOf(s);
index++;
}

System.out.println("最大值："+GetMax(a));
br.close();
fr.close();

}
public static int GetMax(int [] a)
{
int max = a[0];
for (int i = 1; i < a.length; i++) {
if(a[i]>max)
{
max =a[i];
}
}
return max;
}

}

4..从网上下载一个软件，例如QQ：（属于了解）

代码：

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class DownLoad {

public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub

long time = System.currentTimeMillis();
String add = "http://sw.bos.baidu.com/sw-search-sp/software/e6207d37846ba/QQ_8.7.19113.0_setup.exe";
URL url = new URL(add);
HttpURLConnection huc =  (HttpURLConnection) url.openConnection();
InputStream is = huc.getInputStream();
File file = new File("g:/yunke/QQ.exe");
FileOutputStream fos = new FileOutputStream(file,true);

byte []	b = new byte[1024*1024*500];
int len;
double leijia = 0.0;
long total= huc.getContentLengthLong();
while((len = is.read(b) )!=-1)
{
fos.write(b, 0, len);
fos.flush();
leijia+=len;
System.out.println("已下载"+(leijia/total)*100+"%");
}
long time1 = System.currentTimeMillis();
fos.close();

System.out.println("耗时："+(time1-time)+"ms");
}

}

运行结果：



5..从网上下载小说，古诗，然后将内容即中文内容选出，打印出来。（一首古诗）

代码：

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class Download1 {

public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
URL url = new URL("http://www.diyifanwen.com/sicijianshang/tangshisanbaishou/044407104270444076210955.html");
HttpURLConnection hur = (HttpURLConnection) url.openConnection();
InputStream is = hur.getInputStream();

InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String s = "";

File file = new File("g:/a/b/c/3.doc");
FileWriter fw = new FileWriter(file);
BufferedWriter bw = new BufferedWriter(fw);

while((s=br.readLine())!=null)
{
char c[] = s.toCharArray();
String ss= "";
for (int i = 0; i < c.length; i++) {
if(c[i]>255||c[i]<0)
{
ss+=c[i];
}
}
if (!ss.equals("")) {
System.out.println(ss);
bw.write(ss);
bw.flush();
fw.flush();
}

}
br.close();
isr.close();
bw.close();
fw.close();
}

public static String getZhongWen(String temp) {
char[] c = temp.toCharArray();
String str = "";
for (int i = 0; i < c.length; i++) {
if (!(c[i] >= 0 && c[i] <= 255)) {
str += c[i];
}
}
return str;
}

}

运行结果：