java流强化练习

相关类

• InputStream
• OutputStream.
• InputStreamReader
• OutputStreamWriter
• BufferedReader
• BufferedWriter

项目结构

练习代码

import org.junit.Test;

import java.io.*;
import java.math.BigInteger;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class JavaStream {

    /**
     * inputstream  outputstream
     *
     * @throws IOException
     */
    @Test
    public void test0() throws IOException {

        InputStream is = new FileInputStream("/Users/huanghainongye/Desktop/IdeaProjects/java-demo/1.png");
        OutputStream os = new FileOutputStream("/Users/huanghainongye/Desktop/IdeaProjects/java-demo/test/2.png");
        int i = is.read();
        while (i > 0) {
            os.write(i);
            i = is.read();
        }
        is.close();
        os.close();
    }

    /**
     *  ObjectOutputStream 将对象写入文件
     * @throws IOException
     */
    @Test
    public void test1() throws IOException {
        String filepath = "/Users/huanghainongye/Desktop/IdeaProjects/java-demo/lhw.json";
        File file = new File(filepath);
        if(!file.exists()) {
            file.createNewFile();
        }
        FileOutputStream fileOutputStream = new FileOutputStream(filepath);
        ObjectOutputStream oos = new ObjectOutputStream(fileOutputStream);
        oos.writeBoolean(true);
        oos.writeByte((byte) 65);
        oos.writeChar('a');
        oos.writeInt(20131015);
        oos.writeFloat(3.14F);
        oos.writeDouble(1.414D);
        oos.writeUTF("uudd");


        // 写入HashMap对象
        HashMap<String, String> map = new HashMap<String, String>();
        map.put("one", "red");
        map.put("two", "green");
        map.put("three", "blue");
        oos.writeObject(map);

        Bean bean = new Bean();
        bean.setCode(1);
        bean.setDescription("beanData");
        bean.setData(map);
        oos.writeObject(bean);

        oos.close();
        fileOutputStream.close();

    }

    /**
     *  ObjectInputStream 将文件中的对象内容写入内存
     * @throws IOException
     * @throws ClassNotFoundException
     */
    @Test
    public void test2() throws IOException, ClassNotFoundException {
        String filepath = "/Users/huanghainongye/Desktop/IdeaProjects/java-demo/lhw.json";
        FileInputStream fis = new FileInputStream(filepath);
        ObjectInputStream ois = new ObjectInputStream(fis);
        System.out.printf("boolean:%b\n" , ois.readBoolean());
        System.out.printf("byte:%d\n" , (ois.readByte()&0xff));
        System.out.printf("char:%c\n" , ois.readChar());
        System.out.printf("int:%d\n" , ois.readInt());
        System.out.printf("float:%f\n" , ois.readFloat());
        System.out.printf("double:%f\n" , ois.readDouble());
        System.out.printf(ois.readUTF());

        //去读 HashMap对象
        HashMap map = (HashMap)ois.readObject();
        Iterator iterator = map.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry entry = (Map.Entry) iterator.next();
            System.out.printf("%-6s -- %s\n" , entry.getKey(), entry.getValue());
        }

//        // 读取Bean对象
        Bean bean = (Bean) ois.readObject();
        System.out.println("bean:" + bean);

        ois.close();
        fis.close();
    }

    /**
     * BufferedInputStream  BufferedOutputStream 字节缓冲流提升读写效率
     * @throws IOException
     */
    @Test
    public void test3() throws IOException {
        InputStream is = new FileInputStream("/Users/huanghainongye/Desktop/IdeaProjects/java-demo/1.png");
        BufferedInputStream bis = new BufferedInputStream(is);
        OutputStream os = new FileOutputStream("/Users/huanghainongye/Desktop/IdeaProjects/java-demo/test/1333.png");
        BufferedOutputStream bos = new BufferedOutputStream(os);
        byte[] bytes = new byte[1024];
        int read = bis.read(bytes);
        while (read > 0) {
            read = bis.read(bytes);
            bos.write(bytes);
        }

        bis.close();
        is.close();

        bos.close();
        os.close();
    }

    /**
     * FileReader  FileWriter读取 写入文件
     * @throws IOException
     */
    @Test
    public void test4() throws IOException {
        String filePath = "/Users/huanghainongye/Desktop/IdeaProjects/java-demo/text.txt";
        Reader reader = new FileReader(filePath);
        Writer writer = new FileWriter("/Users/huanghainongye/Desktop/IdeaProjects/java-demo/test/text.txt");
        int read = reader.read();
        while (read > 0) {
            writer.write(read);
            read = reader.read();
        }

        reader.close();
        writer.close();
    }


    /**
     * BufferedReader   BufferedWriter  字符流高效读取
     * @throws IOException
     */
    @Test
    public void test5() throws IOException {
        String filePath = "/Users/huanghainongye/Desktop/IdeaProjects/java-demo/text.txt";
        Reader reader = new FileReader(filePath);
        BufferedReader bufferedReader = new BufferedReader(reader);
        Writer writer = new FileWriter("/Users/huanghainongye/Desktop/IdeaProjects/java-demo//test/text2.txt");
        BufferedWriter bufferedWriter = new BufferedWriter(writer);

        String line = null;
        while ((line = bufferedReader.readLine()) != null) {
            System.out.println(line);
            bufferedWriter.append(line);
            bufferedWriter.newLine();
        }
        bufferedWriter.flush();

        bufferedReader.close();
        reader.close();

        bufferedWriter.close();
        writer.close();
    }

    /**
     * InputStream 转 InputStreamReader 输出（字符流比字节流效率高）
     * @throws IOException
     */
    @Test
    public void test6() throws IOException {
        String filePath = "/Users/huanghainongye/Desktop/IdeaProjects/java-demo/text.txt";
        InputStream is = new FileInputStream(filePath);
        InputStreamReader inputStreamReader = new InputStreamReader(is);
        String temp = "";
        int read = inputStreamReader.read();
        while (read > 0) {
            temp+=(char) read;
            read = inputStreamReader.read();
        }

        System.out.println(temp);

        inputStreamReader.close();
        is.close();
    }

    /**
     * InputStream OutputStream.  InputStreamReader   OutputStreamWriter  BufferedReader  BufferedWriter之间的转换
     * @throws IOException
     */
    @Test
    public void test7() throws IOException {
        String filePath = "/Users/huanghainongye/Desktop/IdeaProjects/java-demo/text.txt";
        InputStream is = new FileInputStream(filePath);
        InputStreamReader inputStreamReader = new InputStreamReader(is);
        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
        OutputStream os = new FileOutputStream("/Users/huanghainongye/Desktop/IdeaProjects/java-demo/testext5.txt");
        OutputStreamWriter outputStreamWriter = new OutputStreamWriter(os);
        BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter);

        String temp = null;
        while ((temp = bufferedReader.readLine()) != null) {
            bufferedWriter.append(temp);
            bufferedWriter.newLine();
        }

        bufferedWriter.flush();

        bufferedReader.close();
        inputStreamReader.close();
        is.close();
        bufferedWriter.close();
        outputStreamWriter.close();
        os.close();
    }
}