[英]Converting a String to ByteBuffer in Java
I want to convert an ASCII string to a ByteBuffer and I came across these two approaches:我想将 ASCII 字符串转换为 ByteBuffer,我遇到了这两种方法:
ByteBuffer.wrap(str.getBytes(StandardCharsets.US_ASCII));
and和
StandardCharsets.US_ASCII.encode(str);
What is their difference (maybe in terms of performance too)?它们有什么区别(也许在性能方面也是如此)? Would these produce the same result?这些会产生相同的结果吗?
getBytes
uses the platforms default charset, not necessarily ASCII. getBytes
使用平台默认字符集,不一定是 ASCII。
Encodes this String into a sequence of bytes using the platform's default charset, storing the result into a new byte array.使用平台的默认字符集将此字符串编码为字节序列,并将结果存储到新的字节数组中。
StandardCharsets.US_ASCII.encode
actually uses ASCII. StandardCharsets.US_ASCII.encode
实际上使用 ASCII。
If you use str.getBytes(StandardCharsets.US_ASCII)
, however, then they will be do the same thing on a high level.但是,如果您使用str.getBytes(StandardCharsets.US_ASCII)
,那么它们将在较高级别上执行相同的操作。
After a quick look into their implementations, getBytes
seems to do a very different thing from encode
, so to find out which one is quicker in terms of performance, you'd have to do a benchmark.在快速查看他们的实现之后, getBytes
似乎做了一件与encode
非常不同的事情,所以要找出哪个在性能方面更快,你必须做一个基准测试。
EDIT:编辑:
I wrote a JMH benchmark:我写了一个 JMH 基准测试:
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 10)
@Fork(value = 1)
public class Main {
static final String s = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.";
public static void main (String args[]) throws IOException, RunnerException {
org.openjdk.jmh.Main.main(args);
}
@Benchmark
public void wrap(Blackhole bh) {
bh.consume(ByteBuffer.wrap(s.getBytes(StandardCharsets.US_ASCII)));
}
@Benchmark
public void encode(Blackhole bh) {
bh.consume(StandardCharsets.US_ASCII.encode(s));
}
}
This is the result:这是结果:
Benchmark Mode Cnt Score Error Units
Main.encode avgt 20 2407.242 ± 28.147 ns/op
Main.wrap avgt 20 199.227 ± 4.093 ns/op
So wrap
is a lot faster.所以wrap
要快得多。
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