blocks|key|137449|text|假设您想要在行-主方法中按顺序处理数组的数组，这应该是可行的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|137450|int[][]+arr+=+{+{1,+2,+3},+{4,+5,+6},+{7,+8,+9}+};
IntStream+stream+=+Arrays.stream(arr).flatMapToInt(x+->+Arrays.stream(x));|code-block|syntax|javascript|137451|首先，它调用Arrays.stream(T[])方法(其中T被推断为int[]+)来获取Stream<int[]>，然后Stream#flatMapToInt()方法使用Arrays.stream(int[])方法将每个int[]元素映射到IntStream。|offset|length|style|CODE|137452|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#stream-T:A-|1|http://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#flatMapToInt-java.util.function.Function-|2|http://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#stream-int:A-^0|0|0|6|I|T|1|Y|5|18|D|1O|L|2D|K|32|5|3C|9|6|I|0|1O|L|1|2D|K|2|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@$I|11|J|12|K|L]|$I|13|J|14|K|L]|$I|15|J|16|K|L]|$I|17|J|18|K|L]|$I|19|J|1A|K|L]|$I|1B|J|1C|K|L]|$I|1D|J|1E|K|L]|$I|1F|J|1G|K|L]]|9|@$I|1H|J|1I|1|1J]|$I|1K|J|1L|1|1M]|$I|1N|J|1O|1|1P]]|A|$]]|$1|M|3|-4|5|6|7|1Q|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]|U|$5|P|Q|R|A|$S|V]]|W|$5|P|Q|R|A|$S|X]]]]

Assuming you want to process array of array sequentially in row-major approach, this should work:

<pre><code>int[][] arr = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} };
IntStream stream = Arrays.stream(arr).flatMapToInt(x -&gt; Arrays.stream(x));
</code></pre>

First it invokes the <a href="http://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#stream-T:A-" rel="noreferrer"><code>Arrays.stream(T[])</code></a> method, where <code>T</code> is inferred as <code>int[]</code>, to get a <code>Stream&lt;int[]&gt;</code>, and then <a href="http://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#flatMapToInt-java.util.function.Function-" rel="noreferrer"><code>Stream#flatMapToInt()</code></a> method maps each <code>int[]</code> element to an <code>IntStream</code> using <a href="http://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#stream-int:A-" rel="noreferrer"><code>Arrays.stream(int[])</code></a> method.

blocks|key|137503|text|为了进一步扩展Rohit的答案，可以使用方法引用来略微缩短所需的代码量：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|137504|int[][]+arr+=+{+{1,+2,+3},+
++++++++++++++++{4,+5,+6},
++++++++++++++++{7,+8,+9}+};

IntStream+stream+=+Arrays.stream(arr).flatMapToInt(Arrays::stream);|code-block|syntax|javascript|137505|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

To further expand on Rohit's answer, a method reference can be used to slightly shorten the amount of code required:

<pre><code>int[][] arr = { {1, 2, 3}, 
 {4, 5, 6},
 {7, 8, 9} };

IntStream stream = Arrays.stream(arr).flatMapToInt(Arrays::stream);
</code></pre>

blocks|key|137566|text|要只处理这些元素，可以像Rohit的答案中那样使用flatMap。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|137567|要处理带有索引的元素，您可以使用IntStream.range，如下所示。|137568|import+java.util.stream.IntStream;
import+static+java.util.stream.IntStream.range;

public+class+StackOverflowTest+{
++++public+static+void+main(String...+args)+{
++++++++int[][]+arr+=+{+{+1,+2,+3+},+{+4,+5,+6+},+{+7,+8,+9+}+};
++++++++//+Map+the+two+dimensional+array+with+indices.
++++++++final+IntStream+intStream+=+range(0,+arr.length).flatMap(row+->+range(0,+arr[row].length).map(col+->+{
++++++++++++final+int+element+=+arr[row][col];
++++++++++++//+E.g.+multiply+elements+in+odd+numbered+rows+and+columns+by+two.
++++++++++++return+row+%25+2+==+1+%7C%7C+col+%25+2+==+1+?+element+*+2+:+element;
++++++++}));
++++++++//+Prints+"1+4+3+8+10+12+7+16+9+".
++++++++intStream.forEachOrdered(n+->+System.out.print(n+%2B+"+"));
++++}
}|code-block|syntax|javascript|137569|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/8/docs/api/java/util/stream/IntStream.html#range-int-int-^0|P|7|0|G|F|G|F|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@$9|10|A|11|1|12]]|E|$]]|$1|H|3|I|5|J|7|13|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

To process the elements only, use <code>flatMap</code> as in Rohit's answer.

To process the elements with their indices, you may use <a href="https://docs.oracle.com/javase/8/docs/api/java/util/stream/IntStream.html#range-int-int-" rel="nofollow noreferrer"><code>IntStream.range</code></a> as follows.

<pre><code>import java.util.stream.IntStream;
import static java.util.stream.IntStream.range;

public class StackOverflowTest {
 public static void main(String... args) {
 int[][] arr = { { 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 } };
 // Map the two dimensional array with indices.
 final IntStream intStream = range(0, arr.length).flatMap(row -&gt; range(0, arr[row].length).map(col -&gt; {
 final int element = arr[row][col];
 // E.g. multiply elements in odd numbered rows and columns by two.
 return row % 2 == 1 || col % 2 == 1 ? element * 2 : element;
 }));
 // Prints "1 4 3 8 10 12 7 16 9 ".
 intStream.forEachOrdered(n -&gt; System.out.print(n + " "));
 }
}
</code></pre>

blocks|key|4644203|text|除了前面的回答之外，方法Arrays::stream还返回一个顺序流(请参阅：Oracle+Javadoc。在某些情况下，并行流可能会提高性能。要显式请求并行流，首先需要通过Arrays::asList转换为列表，然后对结果列表调用parallelStream()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4644204|要使用IntStream计算二维int数组的和，可以使用以下代码：|4644205|int[][]+twoDimArray+=+{+{1,+2,+3},+{4,+5,+6},+{7,+8,+9}+};
IntStream+intStream+=+Arrays.asList(twoDimArray)
++++.parallelStream()+++++++++++++++//+"rows"+in+parallel
++++.flatMapToInt(Arrays::stream);++//+"columns"+sequentially
int+sum+=+intStream.sum();++++++++++//+=+45|code-block|syntax|javascript|4644206|为处理外层(行，第一维)而创建的流现在是并行执行的，而内层(列，第二维)的流仍然是顺序的(使用上面提到的Arrays::stream+)。|4644207|根据数组的大小和结构，您可能会看到性能提高了4倍(这是我在自己的测试中测量到的)，或者根本没有提高。如果您的计算是时间关键型的，那么可能值得尝试使用并行流。|4644208|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Arrays.html#stream(T[]%2529)^0|C|E|2F|E|38|G|13|E|0|0|3|9|G|3|0|0|1G|E|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@$9|15|A|16|1|17]]|E|$]]|$1|F|3|G|5|6|7|18|8|@$9|19|A|1A|B|C]|$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|1D|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1E|8|@$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|1H|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

Adding to the previous answers, the method <code>Arrays::stream</code> returns a sequential stream
(see: <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Arrays.html#stream(T[])" rel="nofollow noreferrer">Oracle Javadoc</a>). In some situations, a parallel stream might improve performance. To explicitly request a parallel stream, you first need to convert to a List via <code>Arrays::asList</code>, then call <code>parallelStream()</code> on the resulting List.

To calculate the sum of a two dimensional <code>int</code> array using a <code>IntStream</code>, you can use following code:

<pre><code>int[][] twoDimArray = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} };
IntStream intStream = Arrays.asList(twoDimArray)
 .parallelStream() // "rows" in parallel
 .flatMapToInt(Arrays::stream); // "columns" sequentially
int sum = intStream.sum(); // = 45
</code></pre>

The Stream created for processing the outer layer (rows, first dimension) is now executing in parallel, while the Streams for the inner layer (columns, second dimension) are still sequential (using <code>Arrays::stream</code> mentioned above).

Depending on the size and structure of your array, you might see a performance increase by factor 4 (that's what I measured in my own tests) or none at all. If your calculations are time critical, it might be worth a try to use a parallel Stream.

I am trying to get an <code>IntStream</code> out of an n dimensional <code>int</code> arrays. Is there a nice API way to do it?
I know the concatenate method for two streams.

Stream from two dimensional array in java

我正在尝试从n维int数组中获取IntStream。有没有一种很好的API方法可以做到这一点？我知道两个流的连接方法。

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