Java Reference
In-Depth Information
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// perform calculcations separately
20
Instant separateStart = Instant.now();
long
count = Arrays.stream(values).count();
long
sum = Arrays.stream(values).sum();
long
min = Arrays.stream(values).min().getAsLong();
long
max = Arrays.stream(values).max().getAsLong();
double
average = Arrays.stream(values).average().getAsDouble();
Instant separateEnd = Instant.now();
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// display results
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System.out.println(
"Calculations performed separately"
);
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System.out.printf(
" count: %,d%n"
, count);
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System.out.printf(
" sum: %,d%n"
, sum);
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System.out.printf(
" min: %,d%n"
, min);
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System.out.printf(
" max: %,d%n"
, max);
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System.out.printf(
" average: %f%n"
, average);
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System.out.printf(
"Total time in milliseconds: %d%n%n"
,
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Duration.between(separateStart, separateEnd).toMillis());
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// time sum operation with sequential stream
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LongStream stream1 = Arrays.stream(values);
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System.out.println(
"Calculating statistics on sequential stream"
);
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Instant sequentialStart = Instant.now();
LongSummaryStatistics results1 = stream1.summaryStatistics();
Instant sequentialEnd = Instant.now();
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// display results
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displayStatistics(results1);
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System.out.printf(
"Total time in milliseconds: %d%n%n"
,
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Duration.between(sequentialStart, sequentialEnd).toMillis());
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// time sum operation with parallel stream
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LongStream stream2 = Arrays.stream(values).parallel();
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System.out.println(
"Calculating statistics on parallel stream"
);
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Instant parallelStart = Instant.now();
LongSummaryStatistics results2 = stream2.summaryStatistics();
Instant parallelEnd = Instant.now();
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// display results
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displayStatistics(results1);
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System.out.printf(
"Total time in milliseconds: %d%n%n"
,
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Duration.between(parallelStart, parallelEnd).toMillis());
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}
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// display's LongSummaryStatistics values
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private static void
displayStatistics(LongSummaryStatistics stats)
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{
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System.out.println(
"Statistics"
);
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System.out.printf(
" count: %,d%n"
, stats.getCount());
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System.out.printf(
" sum: %,d%n"
, stats.getSum());
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System.out.printf(
" min: %,d%n"
, stats.getMin());
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System.out.printf(
" max: %,d%n"
, stats.getMax());
Fig. 23.29
|
Comparing performance of sequential and parallel stream operations. (Part 2 of 3.)
