1、IO流异常处理:
IO流异常处理一般可以写得如下这么复杂(面试备用)
- alt + shift + z 直接try-catch ,不过没有加finally
- 因为作用域的问题,需要在外面创建BufferedInputStream对象并且初始化为null(要是不初始化,就不需要关闭了)
- 最后关闭的时候,需要来个嵌套try-catch,去日报关闭一个
代码中try-finally,没加catch(最好还是加吧,反正可以快捷键):
java中异常处理时为什么可以只要try-finally,而可以不要catch
捕获异常,不处理,直接finally扫尾
package cn.njupt;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class file {
public static void main(String[] args) throws IOException {
BufferedInputStream bin = null;
BufferedOutputStream bout = null;
try {
bin = new BufferedInputStream(new FileInputStream("xxx.txt"));
bout = new BufferedOutputStream(new FileOutputStream("yyy.txt"));
int b = 0;
while ((b = bin.read()) != -1) {
bout.write(b);
}
} finally { // alt + shift + z 直接try-catch ,不过没有加finally
try {
if (bin != null)
bin.close();
} finally {
if (bout != null)
bout.close();
}
}
}
}
1.7新版本的IO异常处理:
因为IO流实现了 AutoCloseable的接口,所以可以自动关闭,要是想在try()的括号里写方法,需要实现实现接口(感觉这么写虽然简洁但是没什么章法)
package cn.njupt;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class file {
public static void main(String[] args) throws IOException {
try (BufferedInputStream bin = new BufferedInputStream(new FileInputStream("xxx.txt"));
BufferedOutputStream bout = new BufferedOutputStream(new FileOutputStream("yyy.txt"));)
{
int b = 0;
while ((b = bin.read()) != -1) {
bout.write(b);
}
}
}
}
2、图片加密处理:
可以在write()的时候直接异或一个数,然后再次拷贝的时候需要再次异或同一个数(a异或b两次等于a本身)
package cn.njupt;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
public class file {
public static void main(String[] args) throws IOException {
BufferedInputStream bin = new BufferedInputStream(new FileInputStream("yyy.txt"));
BufferedOutputStream bout = new BufferedOutputStream(new FileOutputStream("zzz.txt"));
int b = 0;
while ((b = bin.read()) != -1) {
bout.write(b ^ 223);
}
bin.close();
bout.close();
}
}
3、输入文件路径并拷贝:
- 键盘输入 (加一个while循环键入和判断)
- 判断是否为文件 File.isFile()
- IO流拷贝
package cn.njupt;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Scanner;
public class file {
public static void main(String[] args) throws IOException {
Scanner sc = new Scanner(System.in);
while (true) {
System.out.println("请输入正确的文件名:");
String line = sc.nextLine();
File file = new File(line);
if (file.isFile()) {
FileInputStream in = new FileInputStream(file);
FileOutputStream out = new FileOutputStream(file.getName());
byte[] arr = new byte[1024 * 8];
int len;
while ((len = in.read(arr)) != -1) {
out.write(arr, 0, len);
}
in.close();
out.close();
break;
} else if(file.isDirectory()){
System.out.println("输入的是文件夹,请重新输入");
}else if(!file.exists()){
System.out.println("不存在此路径,请重新输入");
}
}
}
}
4、在文件中键入内容(遇到quit结束):
package cn.njupt;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Scanner;
public class file {
public static void main(String[] args) throws IOException {
Scanner sc = new Scanner(System.in);
FileOutputStream out = new FileOutputStream("yyy.txt");
while (true) {
System.out.println("请输入想要存储的数据:");
String line = sc.nextLine();
if (line.equals("quit")) {
break;
} else {
byte[] arr = line.getBytes();
out.write(arr);
out.write("\r\n".getBytes());//键入换行
}
}
out.close();
}
}
输出:
我
是
吴彦祖