文件流IO

文件：
创建文档：
File path2=new File(“D:/aqiao/a”);
path2.mkdirs();
文档下创建文件：
File file=new File(“D:/aqiao/a/1.txt”);

    try {
        file.createNewFile();
    }catch (IOException e){
        e.printStackTrace();
    }

删除：
if (file.delete()){
System.out.println(“删除成功”);
}else {
System.out.println(“删除失败”);
}
流：
概念：流是指一连串流动的字符,是以先进先出方式发
送信息的通道

流的分类：
1、流向区分：
输出流：OutputStream和Writer作为基类；
输入流：InputStream和Reader作为基类；
2、处理数据单元划分：
字节流：字节输入流InputStream和字节输出流OutputStream
字符流：字符输入流Reader作为基类和字符输出流Writer作为基类；

FileInputStream读文本文件：
public void get2(){
FileInputStream file=null;
try {
file=new FileInputStream(“D:/aqiao/a/1.txt”);
byte[]b=new byte[500];
int len=-1;
String string="";
while ((len=file.read(b))!=-1){
string+=new String(b,0,len);
}
System.out.println(string);
} catch (Exception e) {
e.printStackTrace();
}finally {
if (file!=null){
try {
file.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

FileOutputStream 写文本文件
public void get3() {
FileOutputStream outputStream = null;
try {
//true表示追加，false表示覆盖
outputStream = new FileOutputStream(“D:/aqiao/a/1.txt”, true);
String words = “你好！！”;
byte[] b = words.getBytes();
System.out.println(“字节大小：” + b.length);
outputStream.write(b);
} catch (Exception e) {
e.printStackTrace();
} finally {
System.out.println(“finally”);
if (outputStream != null) {
try {
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

FileReader读取文件：
public void get4() {
Reader reader=null;
BufferedReader bfReader=null;
try {
reader = new FileReader(“D:/aqiao/a/1.txt”);
bfReader=new BufferedReader(reader);
StringBuffer sbf=new StringBuffer();
String line=null,s=new String();
while ((line=bfReader.readLine())!=null){
// System.out.println(line);
// sbf.append(line+"\n");
s+=line;
}
System.out.println(s);
// System.out.println(sbf.toString());
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
bfReader.close();
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}

}

FileWriter写文件：
public void get5() {
Writer writer=null;
BufferedWriter bfwriter=null;
try {
writer = new FileWriter(“D:/aqiao/a/1.txt”);
bfwriter=new BufferedWriter(writer);
String s=“加油”;
bfwriter.write(s);
// System.out.println(sbf.toString());
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
bfwriter.flush();//清空缓存
bfwriter.close();
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
}

}

通过流读写集合：
写入集合：
public void get7(){
List al=new ArrayList<>();
for (int a=0;a<10;a++){
al.add(“hello”+a);
}
BufferedWriter bw=null;

    try {
        bw=new BufferedWriter(new FileWriter("D:/aq.txt"));
        for (String s:al){
            bw.write(s);
            bw.newLine();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }finally {
        try {
            bw.flush();
            bw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

读取集合：
public void get8(){
BufferedReader br=null;

    try {
        br=new BufferedReader(new FileReader("D:/aq.txt"));
        List<String> al=new ArrayList<>();
        String line;
        while ((line=br.readLine())!=null){
            al.add(line);
        }
        for (String s:al){
            System.out.println(s);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }finally {
        try {
            br.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}