IO流--位元組流

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import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.FileReader;import java.io.FileWriter;import java.io.IOException;import java.io.LineNumberReader;import java.nio.Buffer;public class io {public static void main(String[] args) throws IOException{writeFile();readFile1();readFile2();}//寫入public static void writeFile() throws IOException{FileOutputStream fos = new FileOutputStream("fos.txt");fos.write("abcd".getBytes());fos.close();}//讀出public static void readFile1() throws IOException{FileInputStream fis1 = new FileInputStream("fos.txt");int ch=0;while((ch=fis1.read())!=-1) //一個一個讀{System.out.println((char)ch);}fis1.close();}public static void readFile2() throws IOException{FileInputStream fis2 = new FileInputStream("fos.txt");byte[] buf = new byte[1024]; //緩衝區int len = 0;while((len=fis2.read(buf))!=-1) //以數組大小讀入  傳回值是讀入的個數{System.out.println(new String (buf,0,len));}fis2.close();FileInputStream fis3 = new FileInputStream("fos.txt");//fis2.available 檔案中位元組的個數 int num = fis3.available();//定義一個剛剛好的緩衝區，不能用與檔案很大的 和爆記憶體byte[] buf2 = new byte[fis3.available()];fis3.read(buf2);System.out.println(num+":"+new String(buf2));fis3.close();}}