Java文件读取的四种方法

我会带着你远行 2022-08-21 06:53 165阅读 0赞

package MyFile;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.IOException;
    import java.io.InputStream;
    
    public class FourFunction {
        public static void main(String args[]) {
    /* * InputStream一次只能接受一次文件访问，但是文件路径可以重复利用 * 我想过InputStream能否用数组，结果没能成功。 */
    
            File file = new File("D:" + File.separator + "fileHolder" + File.separator + "Demo1.txt");
            InputStream inS = null;
            try {
                inS = new FileInputStream(file);
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            /////// byte[]不定长//////////
            byte[] bt1 = new byte[1024];
            try {
                inS.read(bt1);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                inS.close();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
    
            System.out.println("第一种方式读取文件内容: " + new String(bt1));
    
            ///////// byte[]不定长循环//////////
            InputStream inS2 = null;
            try {
                inS2 = new FileInputStream(file);
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            byte[] bt2 = new byte[1024];
            int i2 = 0;
            int length = 0;
            try {
                while ((i2 = inS2.read()) != -1) {
                    bt2[length] = (byte) i2;
                    length++;
    
                }
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                inS2.close();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            System.out.println("第二种方式读取文件内容: " + new String(bt2, 0, length));
    
            //////////// byte[]定长////////////////////
            InputStream inS3 = null;
            try {
                inS3 = new FileInputStream(file);
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            byte[] bt3 = new byte[(int) file.length()];
            for (int i = 0; i < bt3.length; i++) {
                try {
                    bt3[i] = (byte) inS3.read();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            try {
                inS3.close();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            System.out.println("第三种方式读取文件内容: " + new String(bt3));
    
            ////////////// byte[]定长循环//////////////////
            InputStream inS4 = null;
            try {
                inS4 = new FileInputStream(file);
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            byte[] bt4 = new byte[(int) file.length()];
            try {
                inS4.read(bt4);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                inS4.close();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            System.out.println("第四种方式读取文件内容: " + new String(bt4));
        }
    
    }