主要分為字節讀取和字符讀取，字節讀取可以一個一個讀取和字節數組讀取，字符讀取同樣之，字符讀取適合文本讀取，字節讀取皆可以

這裏直接上代碼，讀取文件的9個小demo

package com.io;

import org.junit.Test;

import java.io.*;

public class FileTest {
    //1、字節流字節一個一個讀取
    @Test
    public void test() throws IOException{
        InputStream fis = new FileInputStream(new File("E:\\project_test\\src\\com\\io\\readme.txt"));
 
        int len;
        //按字節一個一個讀取
        while ((len = fis.read())!=-1){
            System.out.print((char)len+"\t");
        };
        fis.close();
    }
//輸出結果h    e    l    l    o    w    o    r    l    d   
 
    //2、字節流字節數組讀取
    @Test
    public void test1() throws IOException{
        InputStream fis = new FileInputStream(new File("E:\\project_test\\src\\com\\io\\readme.txt"));
 
        byte[] bytes = new byte[2];
        int len ;
        //按字節數組讀取 bytes存儲的是讀取的數據
        while ((len = fis.read(bytes))!=-1){
            System.out.print((new String(bytes))+"\t");
        };
        fis.close();
    }
//輸出結果 he    ll    ow    or    ld    

    //3、緩沖字節流字節一個一個讀取
    @Test
    public void test2() throws IOException{
 
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(new File("E:\\project_test\\src\\com\\io\\readme.txt")));
        int len ;
        while ((len = bis.read())!=-1){
            System.out.print((char)len+"\t");
        };
        bis.close();
    }

//輸出結果h    e    l    l    o    w    o    r    l    d  

    //4、緩沖字節流字節數組讀取
    @Test
    public void test3() throws IOException{
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(new File("E:\\project_test\\src\\com\\io\\readme.txt")));
        byte[] bytes  = new byte[3];
        int len ;
        //按字節數組讀取 bytes存儲的是讀取的數據
        while ((len = bis.read(bytes))!=-1){
            System.out.print(new String(bytes)+"\t");
        };
        bis.close();
    }
//輸出結果hel    low    orl    drl    

    //5、字符流一個一個讀取
    @Test
    public void test4() throws IOException{
        InputStreamReader isr = new InputStreamReader(new FileInputStream(new File("E:\\project_test\\src\\com\\io\\readme.txt")));
        int len ;
        //按字節數組讀取 bytes存儲的是讀取的數據
        while ((len = isr.read())!=-1){
            System.out.print((char)len+"\t");
        };
        isr.close();
    }


    //6、字符流字符數組讀取
    @Test
    public void test5() throws IOException{
        InputStreamReader isr = new InputStreamReader(new FileInputStream(new File("E:\\project_test\\src\\com\\io\\readme.txt")));
        char[] chars = new char[3];
        int len ;
        //按字節數組讀取 bytes存儲的是讀取的數據
        while ((len = isr.read(chars))!=-1){
            System.out.print(new String(chars)+"\t");
        };
        isr.close();
    }

    //7、緩沖字符流字符一個一個讀取
    @Test
    public void test6() throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(new File("E:\\project_test\\src\\com\\io\\readme.txt"))));
        int len ;
        //按字節數組讀取 bytes存儲的是讀取的數據
        while ((len = br.read())!=-1){
            System.out.print((char)len+"\t");
        };
        br.close();
    }

    //8、緩沖字符流字符數組讀取
    @Test
    public void test7() throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(new File("E:\\project_test\\src\\com\\io\\readme.txt"))));
        char[] chars = new char[3];
        int len ;
        //按字節數組讀取 bytes存儲的是讀取的數據
        while ((len = br.read(chars))!=-1){
            System.out.print(new String(chars)+"\t");
        };
        br.close();
    }

    //9、緩沖字符流按行讀取
    @Test
    public void test8() throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(new File("E:\\project_test\\src\\com\\io\\readme.txt"))));
        //按字節數組讀取 bytes存儲的是讀取的數據
        String str;
        while ( (str = br.readLine())!=null){
            System.out.print(str+"\t");
        };
        br.close();
    }
}

待更。。。。。。。。。。。。。。

java -io 讀取文件操作