我做了一个小的基准测试,发现ObjectOutputStream.writeObject
比ObjectOutputStream.write(byte[] bytes)
快,但我似乎无法找到可能的解释,writeObject
会调用ObjectOutputStream.write(byte[] bytes)
间接
测试代码
public static void main(String[] args) throws Exception {
byte[] bytes = new byte[10000];
for (int i = 0; i < 10000; ++i) {
bytes[i] = (byte) (i % 256);
}
ByteArrayOutputStream out2 = new ByteArrayOutputStream();
try(ObjectOutputStream ostream2 = new ObjectOutputStream(out2)) {
for (int i = 0; i < 10000; ++i) {
ostream2.writeInt(bytes.length);
ostream2.write(bytes, 0, bytes.length);
}
out2.reset();
long start = System.nanoTime();
for (int i = 0; i < 10000; ++i) {
ostream2.writeInt(bytes.length);
ostream2.write(bytes, 0, bytes.length);
}
long end = System.nanoTime();
System.out.println("write byte[] took: " + ((end - start) / 1000) + " micros");
}
ByteArrayOutputStream out = new ByteArrayOutputStream();
try(ObjectOutputStream ostream = new ObjectOutputStream(out)) {
for (int i = 0; i < 10000; ++i) {
ostream.writeObject(bytes);
}
out.reset();
long start = System.nanoTime();
for (int i = 0; i < 10000; ++i) {
ostream.writeObject(bytes);
}
long end = System.nanoTime();
System.out.println("writeObject took: " + ((end - start) / 1000) + " micros");
}
}
输出
写入byte []:15445 micros
writeObject:3111 micros
答案 0 :(得分:6)
ObjectOutputStream.writeObject()
保存书面对象。如果您已经编写了该对象,它只会将句柄写入同一个对象,而不是整个对象。
答案 1 :(得分:1)
我写了一些代码的修改:
public class Test {
public static final int REPS = 10000;
public static void main(String argv[]) throws IOException {
ByteArrayOutputStream out2 = new ByteArrayOutputStream();
try (ObjectOutputStream ostream2 = new ObjectOutputStream(out2)) {
writeBytes(ostream2);
out2.reset();
long start = System.nanoTime();
writeBytes(ostream2);
long end = System.nanoTime();
System.out.println("write byte[] took: " + ((end - start) / 1000) + " micros");
}
ByteArrayOutputStream out = new ByteArrayOutputStream();
try (ObjectOutputStream ostream = new ObjectOutputStream(out)) {
writeObject(ostream);
out.reset();
long start = System.nanoTime();
writeObject(ostream);
long end = System.nanoTime();
System.out.println("writeObject took: " + ((end - start) / 1000) + " micros");
}
}
private static void writeObject(ObjectOutputStream ostream) throws IOException {
for (int i = 0; i < REPS; ++i) {
final byte[] bytes = bytes();
ostream.writeObject(bytes);
}
}
private static void writeBytes(ObjectOutputStream ostream2) throws IOException {
for (int i = 0; i < REPS; ++i) {
final byte[] bytes = bytes();
ostream2.writeInt(bytes.length);
ostream2.write(bytes, 0, bytes.length);
}
}
static byte[] bytes() {
byte[] bytes = new byte[REPS];
for (int i = 0; i < REPS; ++i) {
bytes[i] = (byte) i;
}
return bytes;
}
}
现在结果是
write byte[] took: 51697 micros
writeObject took: 57203 micros