Java 什么'；DataOutputStream和ObjectOutputStream之间的区别是什么？

我正在学习Java中的套接字编程。我见过一些客户机/服务器应用程序示例，其中一些使用

DataOutputStream

，另一些使用

ObjectOutputStream

这两者有什么区别

---

有性能差异吗？

DataInput/OutputStream通常性能更好，因为它更简单。它只能读/写基本类型和字符串

ObjectInput/OutputStream可以读取/写入任何对象类型以及原语。如果要发送复杂的数据，它的效率较低，但使用起来容易得多

---

我认为Object*流是最好的选择，直到您知道它的性能是一个问题。

DataOutputStream

和

ObjectOutputStream

：在处理基本类型时，除了

ObjectOutputStream

创建的头之外没有任何区别

使用

ObjectOutputStream

类，可以将实现

Serializable

的类的实例写入输出流，并可以使用

ObjectInputStream

读回

---

DataOutputStream

只能处理基本类型

只有实现

java.io.Serializable

接口的对象才能使用

ObjectOutputStream

写入流。原始数据类型也可以使用DataOutput中的适当方法写入流。也可以使用writeUTF方法写入字符串。但另一方面，

DataInputStream

允许应用程序以可移植的方式将基本Java数据类型写入输出流

---

这可能对几年后仍在寻找答案的人有用。。。根据我在最近的一个JVM（1.851）上的测试，

ObjectOutput/InputStream

读/写一个庞大的double数组的速度几乎是

DataOutput/InputStream

的2倍

下面是编写1000万项数组的结果（对于100万项，结果基本相同）。为了完整起见，我还包括了文本格式（BufferedWriter/Reader）：

TestObjectStream written 10000000 items, took: 409ms, or 24449.8778 items/ms, filesize 80390629b
TestDataStream written 10000000 items, took: 727ms, or 13755.1582 items/ms, filesize 80000000b
TestBufferedWriter written 10000000 items, took: 13700ms, or 729.9270 items/ms, filesize 224486395b

阅读：

TestObjectStream read 10000000 items, took: 250ms, or 40000.0000 items/ms, filesize 80390629b
TestDataStream read 10000000 items, took: 424ms, or 23584.9057 items/ms, filesize 80000000b
TestBufferedWriter read 10000000 items, took: 6298ms, or 1587.8057 items/ms, filesize 224486395b

我相信Oracle已经对JVM进行了大量优化，以便在上一个Java版本中使用

ObjectStream

s，因为这是写入/读取数据（包括序列化）的最常见方式，因此位于Java性能关键路径上

看来今天再也没有什么理由使用

DataStream

s了。“不要试图智胜JVM”，只需使用最简单的方法，即

ObjectStream

s:）

以下是测试代码：

class Generator {
    private int seed = 1235436537;
    double generate(int i) {
        seed = (seed + 1235436537) % 936855463;
        return seed / (i + 1.) / 524323.;
    }
}

class Data {
    public final double[] array;
    public Data(final double[] array) {
        this.array = array;
    }
}

class TestObjectStream {
    public void write(File dest, Data data) {
        try (ObjectOutputStream out = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(dest)))) {
            for (int i = 0; i < data.array.length; i++) {
                out.writeDouble(data.array[i]);
            }
        } catch (IOException e) {
            throw new RuntimeIoException(e);
        }
    }
    public void read(File dest, Data data) {
        try (ObjectInputStream in = new ObjectInputStream(new BufferedInputStream(new FileInputStream(dest)))) {
            for (int i = 0; i < data.array.length; i++) {
                data.array[i] = in.readDouble();
            }
        } catch (IOException e) {
            throw new RuntimeIoException(e);
        }
    }
}

class TestDataStream {
    public void write(File dest, Data data) {
        try (DataOutputStream out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(dest)))) {
            for (int i = 0; i < data.array.length; i++) {
                out.writeDouble(data.array[i]);
            }
        } catch (IOException e) {
            throw new RuntimeIoException(e);
        }
    }
    public void read(File dest, Data data) {
        try (DataInputStream in = new DataInputStream(new BufferedInputStream(new FileInputStream(dest)))) {
            for (int i = 0; i < data.array.length; i++) {
                data.array[i] = in.readDouble();
            }
        } catch (IOException e) {
            throw new RuntimeIoException(e);
        }
    }
}

class TestBufferedWriter {
    public void write(File dest, Data data) {
        try (BufferedWriter out = new BufferedWriter(new FileWriter(dest))) {
            for (int i = 0; i < data.array.length; i++) {
                out.write(Double.toString(data.array[i]));
                out.newLine();
            }
        } catch (IOException e) {
            throw new RuntimeIoException(e);
        }
    }
    public void read(File dest, Data data) {
        try (BufferedReader in = new BufferedReader(new FileReader(dest))) {
            String line = in.readLine();
            int i = 0;
            while (line != null) {
                if(!line.isEmpty()) {
                    data.array[i++] = Double.parseDouble(line);
                }
                line = in.readLine();
            }
        } catch (IOException e) {
            throw new RuntimeIoException(e);
        }
    }
}

@Test
public void testWrite() throws Exception {
    int N = 10000000;
    double[] array = new double[N];
    Generator gen = new Generator();
    for (int i = 0; i < array.length; i++) {
        array[i] = gen.generate(i);
    }
    Data data = new Data(array);

    Map<Class, BiConsumer<File, Data>> subjects = new LinkedHashMap<>();
    subjects.put(TestDataStream.class, new TestDataStream()::write);
    subjects.put(TestObjectStream.class, new TestObjectStream()::write);
    subjects.put(TestBufferedWriter.class, new TestBufferedWriter()::write);

    subjects.forEach((aClass, fileDataBiConsumer) -> {

        File f = new File("test." + aClass.getName());

        long start = System.nanoTime();
        fileDataBiConsumer.accept(f, data);
        long took = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start);

        System.out.println(aClass.getSimpleName() + " written " + N + " items, took: " + took + "ms, or " + String.format("%.4f", (N / (double)took)) + " items/ms, filesize " + f.length() + "b");
    });
}


@Test
public void testRead() throws Exception {
    int N = 10000000;
    double[] array = new double[N];
    Data data = new Data(array);

    Map<Class, BiConsumer<File, Data>> subjects = new LinkedHashMap<>();
    subjects.put(TestDataStream.class, new TestDataStream()::read);
    subjects.put(TestObjectStream.class, new TestObjectStream()::read);
    subjects.put(TestBufferedWriter.class, new TestBufferedWriter()::read);

    subjects.forEach((aClass, fileDataBiConsumer) -> {
        File f = new File("test." + aClass.getName());

        long start = System.nanoTime();
        fileDataBiConsumer.accept(f, data);
        long took = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start);

        System.out.println(aClass.getSimpleName() + " read " + N + " items, took: " + took + "ms, or " + String.format("%.4f", (N / (double)took)) + " items/ms, filesize " + f.length() + "b");
    });
}

类生成器{
私有整数种子=1235436537；
双生成（int i）{
种子=（种子+1235436537）%936855463；
返回种子/（i+1.）/524323。；
}
}
类数据{
公共最终双[]数组；
公共数据（最终双[]数组）{
this.array=数组；
}
}
类TestObjectStream{
公共无效写入（文件目的地、数据）{
try（ObjectOutputStream out=newobjectoutputstream（new BufferedOutputStream（new FileOutputStream（dest）））{
for（int i=0；i