从代码点编号的 IntStream 中创建一个字符串?

2022-01-12 00:00:00 string char java java-stream charsequence

如果我正在使用 Java 流，并以 IntStream of Unicode 字符的>code point 数字，如何呈现 CharSequence 比如 String?

If I am working with Java streams, and end up with an IntStream of code point numbers for Unicode characters, how can I render a CharSequence such as a String? 

String output = "input_goes_here".codePoints(). ??? ;

我在几个接口上找到了一个 codePoints() 方法 &所有生成代码点的 IntStream 的类.但是我还没有找到任何可以接受相同的构造函数或工厂方法.

I have found a codePoints() method on several interfaces & classes that all generate an IntStream of code points. Yet I have not been able to find any constructor or factory method that accepts the same.

  • CharSequence::codePoints() → IntStream
  • String::codePoints() → IntStream
  • StringBuilder::codePoints() → IntStream

我正在寻找相反的:

➥ 如何从 IntStream 的代码点实例化 String 或 CharSequence 等?

➥ How to instantiate a String or CharSequence or such from an IntStream of code points?

推荐答案

使用IntStream::collect 带有 StringBuilder.

String output = 
    "input_goes_here"
    .codePoints()                            // Generates an `IntStream` of Unicode code points, one `Integer` for each character in the string.
    .collect(                                // Collect the results of processing each code point.
        StringBuilder::new,                  // Supplier<R> supplier
        StringBuilder::appendCodePoint,      // ObjIntConsumer<R> accumulator
        StringBuilder::append                // BiConsumer<R,​R> combiner
    )                                        
    .toString()
;

如果您喜欢更通用的 CharSequence 接口在具体 String，只需将 toString() 放在末尾即可.返回的 StringBuilder 是一个 CharSequence.

If you prefer the more general CharSequence interface over concrete String, simply drop the toString() at the end. The returned StringBuilder is a CharSequence.

IntStream codePointStream = "input_goes_here".codePoints ();
CharSequence output = codePointStream.collect ( StringBuilder :: new , StringBuilder :: appendCodePoint , StringBuilder :: append );

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