FileInputStream FileOutputStream

IO流的分类

   1， 输入流(从硬盘到内存)，输出流(从内存到硬盘)

   2，字节流，字符流(按照数据划分)

所以IO流就是字节输出流，字节输入流，字符输出流，字符输入流

字节输入，输出的超类

InputStream(此抽象类是表示字节输入流的所有类的超类)

   FileInputStream类(从文件系统中的某个文件中获得输入字节 用于读取诸如图像数据之类的原始字节流)

          read()方法   

public static void main(String[] args) throws IOException {		//1,获取一个输入流FileInputStream fis =new FileInputStream("test.txt");//2,从此输入流中读取一个数据字节//int cha =fis.read();//cha表示的是char所对应的ASCII吗，所以是int//System.out.println(cha);//使用循环读取，循环的终止条件是返回-1，说明读到文件的末尾了int cha;//read()相当于Iterator里面的next()是一个一个进行读取while((cha = fis.read())!=-1) {System.out.println((char)cha);//如果读取中文会有问题}

      read(byte[] b)方法        

public static void main(String[] args) throws IOException {		//1,获取一个输入流FileInputStream fis =new FileInputStream("test.txt");//2,从此输入流中读取数据字节byte [] ch =new byte [5];//int len =fis.read(ch);//System.out.println(len+" "+new String(ch));//使用循环读取，循环的终止条件是返回-1，说明读到文件的末尾了int len;while((len = fis.read(ch))!=-1) {System.out.println(len+" "+new String(ch,0,len));	  }

OutputStream(此抽象类是表示输出字节流的所有类的超类)

      FileOutputStream 文件输出流是用于将数据写入 File 或 FileDescriptor 的输出流

          write(byte[] b)将b.length个字节从指定byte数组写入此文件输出流中          

public static void main(String[] args) throws IOException {// TODO Auto-generated method stub//1,创建一个向具有指定 name 的文件中写入数据的输出文件流。如果第二个参数为 true，则将字节写入文件末尾处，而不是写入文件开始处FileOutputStream out =new FileOutputStream("test.txt",true);//如果文件不存在，可以去创建String s ="you are great";//getBytes()使用给定的 charset 将此 String 编码到 byte 序列，并将结果存储到新的 byte 数组。out.write(s.getBytes());System.out.println("完毕");}

复制文件的小案例

public static void main(String[] args) {// TODO Auto-generated method stubFile source =new File("周杰伦 - 超人不会飞.m4a");File rerive =new File("复制版周杰伦 - 超人不会飞.m4a"); FileInputStream fis = null;FileOutputStream  out = null;try {//获取输入流fis =new FileInputStream(source);//获取输出流out =new  FileOutputStream(rerive);//读取数据byte [] cha =new byte[1024];int len;while((len=fis.read(cha))!=-1) {out.write(cha,0,len);}} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally {if(fis!=null) {try {fis.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}if(out!=null) {try {out.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}

 将集合的内容写入到一个文件中小案例

	public static void main(String[] args) throws IOException {// TODO Auto-generated method stubTreeSet<Student>  tree =new TreeSet<Student>(Collections.reverseOrder(new Comparator<Student> (){@Overridepublic int compare(Student o1, Student o2) {// TODO Auto-generated method stubreturn o2.getTotalScore()-o1.getTotalScore();}}));//获取当前操作系统的一个换行String LINE_SEPARATOR =System.getProperty("line.separator");tree.add(new Student("张三",12,34,56));tree.add(new Student("张四",12,34,50));tree.add(new Student("张五",12,34,89));tree.add(new Student("张六",12,30,80));//System.out.println(tree);//新建一个File类File f =new File("stu.txt");//获取输出流FileOutputStream out  =new FileOutputStream(f);//遍历集合for(Student s:tree) {String ss=s.toString();//将文件写入out.write(ss.getBytes());//换行out.write(LINE_SEPARATOR.getBytes());}out.close();}
}
class Student{private String name;private int score1;private int score2;private int score3;private int totalScore;public Student(String name,int score1,int score2,int score3) {this.name =name;this.score1 =score1;this.score2 = score2;this.score3 =score3;this.totalScore =score1+score2+score3;}@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + ((name == null) ? 0 : name.hashCode());result = prime * result + score1;result = prime * result + score2;result = prime * result + score3;result = prime * result + totalScore;return result;}@Overridepublic boolean equals(Object obj) {if (this == obj)return true;if (obj == null)return false;if (getClass() != obj.getClass())return false;Student other = (Student) obj;if (name == null) {if (other.name != null)return false;} else if (!name.equals(other.name))return false;if (score1 != other.score1)return false;if (score2 != other.score2)return false;if (score3 != other.score3)return false;if (totalScore != other.totalScore)return false;return true;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getScore1() {return score1;}public void setScore1(int score1) {this.score1 = score1;}public int getScore2() {return score2;}public void setScore2(int score2) {this.score2 = score2;}public int getScore3() {return score3;}public void setScore3(int score3) {this.score3 = score3;}public int getTotalScore() {return totalScore;}public void setTotalScore(int totalScore) {this.totalScore = totalScore;}@Overridepublic String toString() {return "Student [name=" + name + ", score1=" + score1 + ", score2=" + score2 + ", score3=" + score3+ ", totalScore=" + totalScore + "]";}}

文件复制小案例

 * 需求：将一个目录中的所有以html结尾的文件统一复制到一个sourcecode的文件夹中
 * 1，遍历当前目录中的所有文件和文件夹
 * 2，选择是html结尾的文件(文件过滤)
 * 3，复制文件到统一目录

public class CopyJavaFile {
/*** 需求：将一个目录中的所有以html结尾的文件统一复制到一个sourcecode的文件夹中* 1，遍历当前目录中的所有文件和文件夹* 2，选择是html结尾的文件(文件过滤)* 3，复制文件到统一目录*/public static void main(String[] args) throws IOException {// TODO Auto-generated method stub//新建File类File source =new File("D:\\eclipse");File aim =new File("sourcecode");//如果目录不存在，创建一个目录if(!aim.exists()) {aim.mkdir();}//来个集合LinkedList<File>  queue =new LinkedList<File>();//进队queue.offer(source);while(!queue.isEmpty()) {File am =queue.poll();File [] files =am.listFiles();for(File f:files) {if(f.isDirectory()) {queue.offer(f);}else {//如果文件的后缀名是HTML,则进行复制if(f.getName().endsWith(".html")) {copy(aim,f);}}}}}private static void copy(File aim, File f) throws IOException {// TODO Auto-generated method stub//拷贝后的文件，路径名是aim+f.getName()File javaFile =new  File(aim,f.getName());//获得输入流FileInputStream fis =new FileInputStream(f);//获得输出流FileOutputStream out =new FileOutputStream(javaFile);int len;byte [] bf =new byte [1024];while((len = fis.read(bf))!=-1) {out.write(bf,0,len);}fis.close();out.close();}}

文件复制的总结

1，创建文件类

 File  source =new File(directory)

File  aim =new File(directory2)

2，获取输入流,输出流

FileInputStream f =new   FileInputStream(source);

FileOutputStream f1=new   FileOutputStream(aim);

3，每次一1024K进行读和写

int len;

byte [] bf =new byte[1024];

while((len= f.read(bf))!=-1){

//写入

f1.write(bf,0,len);

}

4,关闭流

f.close();

f1.close();