Java 8 Streams：IntStream 到 String
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Java 8 Streams: IntStream to String
提问by yyoon
In Java 8 streams API, calling chars()on any Stringobject returns an IntStreamobject containing all the characters.
在 Java 8 流 API 中，调用chars()任何String对象都会返回一个IntStream包含所有字符的对象。
What would be the correct way to convert the returned IntStreamobject back to a String? Calling toArray()would give me an int[], which is not accepted by any of the Stringconstructor.
将返回的IntStream对象转换回 a的正确方法是String什么？调用toArray()会给我一个int[]，它不被任何String构造函数接受。
采纳答案by Jon Skeet
You can use toArray(), then the String(int[], int, int)constructor. This isn't entirely satisfactory as chars()is specified to return UTF-16 code units, basically:
您可以使用toArray(), 然后是String(int[], int, int)构造函数。这并不完全令人满意，因为chars()指定返回 UTF-16 代码单元，基本上：
Returns a stream of int zero-extending the char values from this sequence. Any char which maps to a surrogate code point is passed through uninterpreted.
返回一个 int 流，零扩展此序列中的 char 值。映射到代理代码点的任何字符都未经解释地传递。
Using codePoints()instead would be more in-keeping with this constructor, which expects code points rather than UTF-16 code units. Otherwise (with chars) if your original string doescontain surrogate pairs, you may find you get an error - I haven't tried it, but it would make sense.
使用它codePoints()会更符合这个构造函数，它需要代码点而不是 UTF-16 代码单元。否则 (with chars) 如果您的原始字符串确实包含代理对，您可能会发现您收到错误 - 我没有尝试过，但它会有意义。
I don't know of a simple way of doing this without converting to an array first.
我不知道不先转换为数组的简单方法。
回答by rmuller
This is an other idea:
这是另一个想法：
@Test
public void testIntStreamSequential() {
final String testString = "testmesoftly";
IntStream is = testString.chars();
String result = is.collect(
StringBuilder::new,
(sb, i) -> sb.append((char)i),
StringBuilder::append
).toString();
assertEquals(testString, result);
}
@Test
public void testIntStreamParallel() {
final String testString = "testmesoftly";
IntStream is = testString.chars();
String result = is.parallel().collect(
StringBuilder::new,
(sb, i) -> sb.append((char)i),
StringBuilder::append
).toString();
assertEquals(testString, result);
}
Note that using a dedicated Collectoras proposed by @Lii is not very efficient, because of the boxing so you should use this three argument construct (thanks @holger)
请注意，使用Collector@Lii 建议的专用不是很有效，因为装箱所以你应该使用这三个参数构造（感谢@holger）
回答by Edwin Dalorzo
I am pretty sure there must be many ways to do it, but another way is by using a StringWriter:
我很确定一定有很多方法可以做到这一点，但另一种方法是使用StringWriter：
IntStream in = "It was the best of times".chars();
StringWriter sw = new StringWriter();
in.forEach(sw::write);
System.out.println(sw.toString());
This all could also be expressed in a collector as:
这一切也可以在收集器中表示为：
IntStream in = "It was the best of times".chars();
String text = in.collect(
StringWriter::new,
StringWriter::write,
(swl, swr) -> swl.write(swr.toString())).toString();
System.out.println(text);
回答by Sufiyan Ghori
using StringBuilder's appendCodePointmethod would do the trick as well,
usingStringBuilder的appendCodePoint方法也可以解决问题，
IntStream in = "Convert me to a String".codePoints();
String intStreamToString = in.collect(StringBuilder::new,
StringBuilder::appendCodePoint, StringBuilder::append)
.toString();
System.out.println(intStreamToString);
