英文:
Process string using Java streams
问题
我需要一些指导。我不确定如何使用Java Streams将示例文本文件读入对象数组。流是否提供从文件读取的字符串中正确输出字符位置的功能？
我正在使用Java I/O读取文件，然后将内容作为字符串传递给此函数以创建Square对象的数组...
这是否可以使用Java 8 Stream来创建对象数组？如果可以，怎么做？谢谢。
英文:
I am in need of some guidance. I am not sure how to go about reading in the sample text file into an array of objects using Java Streams. Does stream provide a functionality to correctly output a position of the character from a string that it reads from the file?
I am reading a file using Java I/O and then passing the content as string to this function to create array of Squares....
Can this creation of Array of Objects be done using Java 8 Stream ? If so How please. Thank you.
答案1
得分: -1
使用Java Streams，您可以像这样进行操作：
AtomicInteger row = new AtomicInteger(-1);
// 使用这个来计算特定字符的数量：
AtomicInteger someCount = new AtomicInteger();
try (Stream<String> stringStream = Files.lines(Paths.get("yourFile.txt"))) { // 从文件中读取所有行到字符串流中
// 这个函数创建了每一行的Square对象数组
Function<String, Square[]> mapper = (s) -> {
AtomicInteger col = new AtomicInteger();
row.incrementAndGet();
return s.chars()
.mapToObj(i -> {
// 如果字符满足条件，增加计数器
if((char)i == 'M')
someCount.incrementAndGet();
return new Square(row.get(), col.getAndIncrement(), (char)i);
})
.toArray(i -> new Square[s.length()]);
};
// 使用上面的映射函数对所有行进行流式处理，您可以将它们收集到List<Square[]>中，然后将此List转换为Square对象的数组
Square[][] squares = stringStream
.map(mapper)
.collect(Collectors.toList()).toArray(new Square[0][]);
}
回答您的第二个问题：如果您有一个Square[]数组，并且想要找到第一个val == 'M'的Square，您可以这样做：
Optional<Square> optSquare = Stream.of(squares).flatMap(Stream::of).filter(s -> s.getVal() == 'M').findFirst();
// 如果没有匹配条件的Square，mySquare将为null
Square mySquare = optSquare.orElse(null);
英文:
Using java streams you could do something like this:
AtomicInteger row = new AtomicInteger(-1);
// count specific characters with this:
AtomicInteger someCount = new AtomicInteger();
try (Stream<String> stringStream = Files.lines(Paths.get("yourFile.txt"))) { // read all lines from file into a stream of strings
// This Function makes an array of Square objects of each line
Function<String, Square[]> mapper = (s) -> {
AtomicInteger col = new AtomicInteger();
row.incrementAndGet();
return s.chars()
.mapToObj(i -> {
// increment counter if the char fulfills condition
if((char)i == 'M')
someCount.incrementAndGet();
return new Square(row.get(), col.getAndIncrement(), (char)i);
})
.toArray(i -> new Square[s.length()]);
};
// Now streaming all lines using the mapper function from above you can collect them into a List<Square[]> and convert this List into an Array of Square objects
Square[][] squares = stringStream
.map(mapper)
.collect(Collectors.toList()).toArray(new Square[0][]);
}
Answering your second question: If you have an array of Square[] and want to find the first Square with val == 'M' you could do this:
Optional<Square> optSquare = Stream.of(squares).flatMap(Stream::of).filter(s -> s.getVal() == 'M').findFirst();
// mySquare will be null if no Square was matching condition
Square mySquare = optSquare.orElse(null);
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