File 类
比较
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| String fileName = "d:" + File.separator + "b.txt";
File f1 = new File(fileName);
File f2 = new File(fileName);
System.out.println(f1 == f2); // false 比较引用
System.out.println(f1.equals(f2)); // true 比较文件路径
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字节流：InputStream、OutputStream
字符流（处理文本）：Reader、Writer
节点流：可单独处理数据
处理流：依赖其他流处理数据
问题
文本文件a.txt内容如下：
读取a.txt内容时每次读取三个字符输出不正确
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| char[] buffer = new char[3];
int len;
while ((len = fileReader.read(buffer, 0, buffer.length)) > -1) {
System.out.println(new String(buffer, 0, len) + ":");
}
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转换流：转换字节流和字符流
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| public static void IOStreamRW() throws IOException {
String fileName = "d:" + File.separator + "a.txt";
String newFileName = "d:" + File.separator + "new.txt";
FileInputStream fis = new FileInputStream(fileName);
//InputStreamReader isr = new InputStreamReader(fis);
InputStreamReader isr = new InputStreamReader(fis, "GBK");//默认utf-8 windows记事本显示ANSI表示使用系统编码（我的电脑是GBK）
BufferedReader br = new BufferedReader(isr);
FileOutputStream fos = new FileOutputStream(newFileName);
OutputStreamWriter osw = new OutputStreamWriter(fos, "utf-8");
BufferedWriter bw = new BufferedWriter(osw);
int r;
char[] chars = new char[1024];
/**
* 1
*/
//while ((r = isr.read(chars, 0, chars.length)) > -1) {
// osw.write(chars, 0, r);
//}
//osw.close();
//isr.close();
/**
* 2 bufferedReader、bufferedWriter
*/
while ((r = br.read(chars, 0, chars.length)) > -1) {
bw.write(chars, 0, r);
}
bw.close();
br.close();
}
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数据流：处理基本数据类型和字符串
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| public static void DataIOputStream() throws IOException {
String fileName = "d:" + File.separator + "s.txt";
File file = new File(fileName);
FileOutputStream fos = new FileOutputStream(file);
DataOutputStream dos = new DataOutputStream(fos);
dos.writeUTF("你好哈哈");
dos.writeInt(10);
dos.writeBoolean(true);
dos.writeDouble(1.98);
dos.writeUTF("你好嘻嘻");
FileInputStream fis = new FileInputStream(file);
DataInputStream dis = new DataInputStream(fis);
//按顺序读取
System.out.println(dis.readUTF());
System.out.println(dis.readInt());
System.out.println(dis.readBoolean());
System.out.println(dis.readDouble());
System.out.println(dis.readUTF());
}
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对象流做序列化反序列化
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| public static void ObjectIOputStream() throws IOException, ClassNotFoundException {
String fileName = "d:" + File.separator + "ois.txt";
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(fileName));
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(fileName));
oos.writeObject(new Person(1, "vvf"));
oos.close();
System.out.println(ois.readObject());
}
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声明serialVersionUID 说明版本兼容性问题（默认会自动生成，修改类时会发生变化）
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| class Person implements Serializable{
public Person() {
}
private static final long serialVersionUID = 643382323274886977L;
public Person(int age, String name) {
this.age = age;
this.name = name;
}
int age;
String name;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
//@Override
//public String toString() {
// return "Person{" +
// "age=" + age +
// ", name='" + name + '\'' +
// '}';
//}
}
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transient 修饰不可序列化的属性
静态属性也不会被序列化
RandomAccessFile
分段读取文件