Java中IO之文件的读取详细解读

谁借莪１个温暖的怀抱￠ 2022-02-26 10:28 144阅读 0赞

## 一、整个IO类的结构图为： ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1cHJlemhlbmc_size_16_color_FFFFFF_t_70][]

## 二、测试文件的读取： ##

###  1.先创建一个txt文件，保存时选择UTF-8编码格式 ###

![2019032915462060.png][]

### 2.创建测试类进行测试  ###

package cn.mesmile.io;
    
    import org.junit.Test;
    
    import java.io.*;
    
    /**
     * @date 2019-03-29
     */
    public class IOTest {
        /**
         * 字符流读出来的是 char[] 或者 string
         * 字节流读出来的是 byte[]
         *
         * 字符流：Reader        Writer
         * 字节流：InputStream   OutputStream
         *
         * @throws IOException
         */
        @Test
        public void testFileReader () throws IOException {
            // 【字符流】直接读取文件
            FileReader fileReader = new FileReader("D:\\test.txt");
            int ch = 0;
            while ((ch=fileReader.read())!=-1){
                System.out.println((char) ch);
            }
        }
        @Test
        public void testInputStreamReader () throws Exception {
            // 【字节流】转换成【字符流】      Stream 作为中间桥梁       【字节流】可以指定：读取时候的编码方式
            InputStreamReader inputStreamReader = new InputStreamReader(new FileInputStream("D:\\test.txt"),"UTF-8");
            char [] buffer = new char[1024];
            int ch = 0 ;
            while ((ch=inputStreamReader.read(buffer))!=-1){
                System.out.println(buffer);
            }
        }
        @Test
        public void testBufferedReader () throws Exception {
            //        【字符缓存流】中存取【字符流】                        【字节流】转换成【字符流】
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream("D:\\test.txt"), "UTF-8"));
            String string =  null;
            while ((string=bufferedReader.readLine())!=null){
                System.out.println(string);
            }
        }
        @Test
        public void testFileInputStream () throws Exception {
            File file = new File("D:\\test.txt");
            // 【字节流】直接读取文件
            FileInputStream fileInputStream = new FileInputStream(file);
            byte [] bytes = new byte[1024];
            int ch = 0;
            while ((ch=fileInputStream.read(bytes))!=-1){
                System.out.println(bytes);
            }
        }
        @Test
        public void test () throws Exception {
            // 【缓存字符流】中存取【字符流】
            BufferedReader bufferedReader = new BufferedReader(new FileReader("D:\\test.txt"));
            String string = null;
            while ((string=bufferedReader.readLine())!=null){
                System.out.println(string);
            }
        }
    }

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[2019032915462060.png]: /images/20220226/ca6de84da0a6417c8ac47bf895569a17.png