Java编程思想--I/O系统
1，File类
既能代表一个特定文件的名称，又能代表一个目录下的一组文件的名称。如果它指向的是一个文件集，可以对词集合调用list()方法，返回一个字符数组。
例1
package FileTest;
import java.io.File;
public class DirList {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
File filedir=new File("/home/hadoop/Data/luceneData");
File[] textFiles=filedir.listFiles();
for(File file :textFiles){
System.out.println(file.getAbsolutePath());
System.out.println(file.getName());
}
}
}结果
/home/hadoop/Data/luceneData/txt1.txt txt1.txt /home/hadoop/Data/luceneData/txt2.txt txt2.txt /home/hadoop/Data/luceneData/txt5.txt txt5.txt /home/hadoop/Data/luceneData/txt4.txt txt4.txt /home/hadoop/Data/luceneData/txt3.txt txt3.txt输出文件的绝对路径和文件名
2，输入和输出
缓冲输入文件
package InOutPut;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOError;
import java.io.IOException;
public class BufferedInputFile {
/**
* @param args
*/
public static String read(String filename) throws IOException{
BufferedReader in=new BufferedReader(new FileReader(filename));
String s;
StringBuilder sb =new StringBuilder();
while((s=in.readLine())!=null){
sb.append(s+"\n");
}
in.close();
return sb.toString();
}
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
System.out.println(read("./src/FileTest/DirList.java"));
}
}
结果
package FileTest;
import java.io.File;
import java.io.IOException;
public class DirList {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
File filedir=new File("/home/hadoop/Data/luceneData");
File[] textFiles=filedir.listFiles();
for(File file :textFiles){
System.out.println(file.getAbsolutePath());
System.out.println(file.getCanonicalPath());
System.out.println(file.getName());
}
}
}
从内存输入
package InOutPut;
import java.io.IOException;
import java.io.StringReader;
public class MemoryInput {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
StringReader inReader=new StringReader(BufferedInputFile.read("./src/FileTest/DirList.java"));
int c;
while((c=inReader.read())!=-1){
System.out.println((char)c);
}
System.out.println(BufferedInputFile.read("./src/FileTest/DirList.java"));
}
}
结果
package InOutPut;
import java.io.IOException;
import java.io.StringReader;
public class MemoryInput {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
StringReader inReader=new StringReader(BufferedInputFile.read("./src/FileTest/DirList.java"));
int c;
while((c=inReader.read())!=-1){
System.out.println((char)c);
}
System.out.println(BufferedInputFile.read("./src/FileTest/DirList.java"));
}
}
基本的文件输出
package InOutPut;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringReader;
public class BasicFileOutput {
static String file ="Output.out";
/**
* @param args
*/
public static void main(String[] args) throws IOException{
// TODO Auto-generated method stub
BufferedReader in= new BufferedReader(new StringReader(BufferedInputFile.read("./src/FileTest/DirList.java")));
PrintWriter out=new PrintWriter(file);
int lineCount=1;
String s;
while((s=in.readLine()) !=null){
out.println(lineCount++ + ": "+s);
}
out.close();
System.out.println(BufferedInputFile.read(file));//从内存中读取
System.out.println(BufferedInputFile.read("./Output.out"));
}
}
结果
1: package FileTest;
2:
3: import java.io.File;
4: import java.io.IOException;
5:
6: public class DirList {
7:
8: /**
9: * @param args
10: * @throws IOException
11: */
12: public static void main(String[] args) throws IOException {
13: // TODO Auto-generated method stub
14: File filedir=new File("/home/hadoop/Data/luceneData");
15: File[] textFiles=filedir.listFiles();
16: for(File file :textFiles){
17: System.out.println(file.getAbsolutePath());
18: System.out.println(file.getCanonicalPath());
19: System.out.println(file.getName());
20: }
21:
22: }
23:
24: }
1: package FileTest;
2:
3: import java.io.File;
4: import java.io.IOException;
5:
6: public class DirList {
7:
8: /**
9: * @param args
10: * @throws IOException
11: */
12: public static void main(String[] args) throws IOException {
13: // TODO Auto-generated method stub
14: File filedir=new File("/home/hadoop/Data/luceneData");
15: File[] textFiles=filedir.listFiles();
16: for(File file :textFiles){
17: System.out.println(file.getAbsolutePath());
18: System.out.println(file.getCanonicalPath());
19: System.out.println(file.getName());
20: }
21:
22: }
23:
24: }
3，I/O
从标准输入中读取
package IO;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class Echo {
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
BufferedReader stdin =new BufferedReader(new InputStreamReader(System.in));
String s;
while((s=stdin.readLine()) != null && s.length() !=0){
System.out.println(s);
}
}
}
结果
哈哈
哈哈
输出
package IO;
import java.io.PrintWriter;
public class ChangeSystemOut {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
PrintWriter out =new PrintWriter(System.out,true);
out.println("Hello,world!");
}
}
结果
Hello,world!