java.io流
io流
常用的文件操作
创建文件
//1.
File file = new File(pathname);
file.createNewFile();
//2.
File file = new File(parentFile(File), fileName(String));
file.createNewFile();
//3.
File file = new File(parentPath(String), fileName(String));
获取文件信息
getName(),getAbsolutePath(),getParent(),length(),exists(),isFile(),isDirectory()
创建/删除文件
mkdir(),mkdirs(),delete()
流的分类
字节流
字节输入流(InputStream)
FileInputStream
演示
public class Test01 {
public static void main(String[] args) {
String name = "src\\1.txt";
int read = 0;
try {
FileInputStream fileInputStream = new FileInputStream(name);
while((read = fileInputStream.read())!=-1){
System.out.print((char)read);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
System.out.println();
try {
byte[] bytes = new byte[1024];
FileInputStream fileInputStream = new FileInputStream(name);
while((read = fileInputStream.read(bytes))!=-1){
System.out.println(new String(bytes));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
字节输出流(OutputStream)
FileOutputStream
实例
String name = "src\\1.txt";
try{
FileOutputStream fileOutputStream = new FileOutputStream(name);
fileOutputStream.write("asdf".getBytes());
}catch(Exception e){
e.printStackTrace();
}
字符流
字符输入流(Reader)
FileReader
//1.第一种连接方式
int temp = 0;
FileReader fileReader = new FileReader("1.txt");
while((temp = fileReader.read()) != -1){
System.out.print((char)temp);
}
fileReader.close();
//2.第二种两种方式
char[] temp = new char[8];
int i = 0;
FileReader fileReader = new FileReader("1.txt");
while((i = fileReader.read(temp)) != -1){
System.out.print(new String(temp, 0, i));
}
fileReader.close();
字符输出流(Writer)
FileWriter
String thing = "哈哈哈";
FileWriter j = new FileWriter("1.txt", true);
j.write(thing.toCharArray());
j.close();
包装流
包装流(buffered)
字符处理流
注意:
bufferedReader和bufferedWriter是按照字符操作,不要去操作二进制文件例如声音,视频,pdf,doc文档等
BufferedReader(包装reader实现类的节点流)
String name = "1.txt";
//创建字节流
FileReader reader = new FileReader(name);
BufferedReader buffer = new BufferedReader(reader);
String str;
int count = 0;
while((str = buffer.readLine())!=null){
System.out.println(str);
}
//关闭包装流,里边的字节流底层自动关闭
buffer.close();
BufferedWriter(包装writer实现类的节点流)
String name = "1.txt";
FileWriter writer = new FileWriter(name, true);
BufferedWriter buffer = new BufferedWriter(writer);
buffer.write("你好爱豆if哈子双方都一杭州市地方");
buffer.newLine();
buffer.write("你好爱豆if哈子双方都一杭州市地方");
buffer.newLine();
buffer.write("你好爱豆if哈子双方都一杭州市地方");
buffer.newLine();
buffer.flush();
字节处理流
BufferedInputStream
BufferedOutputStream
实例
String s1 = "1.txt";//源文件
String s2 = "4.txt";//拷贝文件
FileInputStream fileInputStream = new FileInputStream(s1);
FileOutputStream fileOutputStream = new FileOutputStream(s2);
BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream);
BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fileOutputStream);
byte[] bytes = new byte[1024];
int len = 0;
while((len = bufferedInputStream.read(bytes)) != -1){
bufferedOutputStream.write(bytes, 0, len);
}
bufferedInputStream.close();
bufferedOutputStream.close();
序列化
-
序列化就是在保存数据时,保存数据的值和数据类型
-
反序列化就是在恢复数据时,恢复数据的值和数据类型
-
如果需要类可序列化,需要该类实现以下两个接口之一
- Serializable //标记接口
- Externalizable //该接口需要实现方法
包装流(Object)
ObjectOutStream
String name = "5.txt";
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(name));
objectOutputStream.writeInt(100);
objectOutputStream.writeBoolean(true);
objectOutputStream.writeChar('a');
objectOutputStream.writeUTF("wangafasdf");
objectOutputStream.close();
ObjectInputStream
String name = "5.txt";
ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream(name));
System.out.println(objectInputStream.readInt());
System.out.println(objectInputStream.readBoolean());
System.out.println(objectInputStream.readChar());
System.out.println(objectInputStream.readUTF());
objectInputStream.close();
注意事项
- 读写顺序要一致
- 要求实现序列化或反序列化对象,需要实现Serializable
- 序列化对选时,默认奖励不拿所有属性都序列化,但除了static或者transient修饰的对象修饰的成员
- 序列化对象时,要求里面所有属性的烈性也需要实现序列化接口
- 序列化的类中建议添加SeriaIVersionUID,为了提高版本的兼容性
- 序列化具备可继承性,也就是如果某类已经实现序列化,则他的所有子类也已经默认实现了序列化.
转化流
-
转换流InputStreamReader和OutputSteamWriter
-
InputStreamReader:Reader的子类,可以将InputStream包装成Reader
-
OutputStreamWriter:Writer的子类,实现将OutputStream包装成Writer
-
档处理纯文本数据时,如果使用字符流效率更高,并且可以有效解决中文的问题,所以建议将字节流转换成字符流
-
可以在使用指定编码格式比如utf-8,gbk,gb2312,ISO8859-1
InputStreamReader
String name = "6.txt";
BufferedReader j = new BufferedReader(new InputStreamReader(new FileInputStream(name), "gbk"));
String str;
while((str = j.readLine()) != null){
System.out.println(str);
}
j.close();
//说明:文件是gbk编码,idea是utf-8,所以使用转化流转换
OutputStreamWriter
String name = "7.txt";
BufferedWriter k = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(name), "utf-8"));
k.write("和嘿嘿");
k.close();
//将字符串以utf-8的方式存储
打印流
PrintStream
String name = "8.txt";
System.setOut(new PrintStream(name));
PrintStream i = System.out;
i.println("afsasdfads");
i.close();
//改变System.out指向,字符打印到文件中
printWriter
String name = "9.txt";
PrintWriter i = new PrintWriter(new PrintWriter(name));
i.println("afsasdfads");
i.close();
配置文件Properties
读取
String name = "db.properties";
Properties properties = new Properties();
properties.load(new FileReader(name));
properties.list(System.out);
System.out.println(properties.getProperty("username"));
创建/修改
当文件没有时为创建,有文件时为修改
String name = "new.properties";
Properties properties = new Properties();
properties.setProperty("username", "谁谁谁");
properties.setProperty("password", "123456");
properties.store(new FileWriter(name), null);
