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+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   - Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *
+ *   - Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ *   - Neither the name of Oracle nor the names of its
+ *     contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * This source code is provided to illustrate the usage of a given feature
+ * or technique and has been deliberately simplified. Additional steps
+ * required for a production-quality application, such as security checks,
+ * input validation, and proper error handling, might not be present in
+ * this sample code.
+ */
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.*;
+import java.util.function.*;
+import java.util.regex.Pattern;
+import java.util.stream.Collector;
+import java.util.stream.Collectors;
+
+import static java.lang.Double.parseDouble;
+import static java.util.stream.Collectors.*;
+
+/**
+ * CSVProcessor is a tool for processing CSV files. There are several
+ * command-line options. Consult the {@link #printUsageAndExit} method for
+ * instructions and command line parameters. This sample shows examples of the
+ * following features:
+ * <ul>
+ * <li>Lambda and bulk operations. Working with streams: map(...), filter(...),
+ * sorted(...) methods. The collect(...) method with different collectors:
+ * Collectors.maxBy(...), Collectors.minBy(...), Collectors.toList(),
+ * Collectors.toCollection(...), Collectors.groupingBy(...),
+ * Collectors.toDoubleSummaryStatistics(...), and a custom Collector.</li>
+ * <li>Static method reference for printing values.</li>
+ * <li>Try-with-resources feature for closing files.</li>
+ * <li>Switch by String feature.</li>
+ * <li>Other new APIs: Pattern.asPredicate(), BinaryOperator
+ * BufferedReader.lines(), Collection.forEach(...), Comparator.comparing(...),
+ * Comparator.reversed(), Arrays.stream(...).</li>
+ * </ul>
+ *
+ */
+public class CSVProcessor {
+
+    //Number of characters that may be read
+    private static final int READ_AHEAD_LIMIT = 100_000_000;
+
+    /**
+     * The main method for the CSVProcessor program. Run the program with an
+     * empty argument list to see possible arguments.
+     *
+     * @param args the argument list for CSVProcessor.
+     */
+    public static void main(String[] args) {
+        if (args.length < 2) {
+            printUsageAndExit();
+        }
+        try (BufferedReader br = new BufferedReader(
+                Files.newBufferedReader(Paths.get(args[args.length - 1])))) {
+            //Assume that the first line contains column names.
+            List<String> header = Arrays.stream(br.readLine().split(","))
+                    .map(String::trim).collect(toList());
+            //Calculate an index of the column in question.
+            int column = getColumnNumber(header, args[1]);
+            switch (args[0]) {
+                case "sort":
+                    verifyArgumentNumber(args, 4);
+                    //Define the sort order.
+                    boolean isAsc;
+                    switch (args[2].toUpperCase()) {
+                        case "ASC":
+                            isAsc = true;
+                            break;
+                        case "DESC":
+                            isAsc = false;
+                            break;
+                        default:
+                            printUsageAndExit("Illegal argument" + args[2]);
+                            return;//Should not be reached.
+                    }
+                    /*
+                     * Create a comparator that compares lines by comparing
+                     * values in the specified column.
+                     */
+                    Comparator<String> cmp
+                            = Comparator.comparing(str -> getCell(str, column),
+                                    String.CASE_INSENSITIVE_ORDER);
+                    /*
+                     * sorted(...) is used to sort records.
+                     * forEach(...) is used to output sorted records.
+                     */
+                    br.lines().sorted(isAsc ? cmp : cmp.reversed())
+                            .forEach(System.out::println);
+                    break;
+                case "search":
+                    verifyArgumentNumber(args, 4);
+                    /*
+                     * Records are filtered by a regex.
+                     * forEach(...) is used to output filtered records.
+                     */
+                    Predicate<String> pattern
+                            = Pattern.compile(args[2]).asPredicate();
+                    br.lines().filter(str -> pattern.test(getCell(str, column)))
+                            .forEach(System.out::println);
+                    break;
+                case "groupby":
+                    verifyArgumentNumber(args, 3);
+                    /*
+                     * Group lines by values in the column with collect(...), and
+                     * print with forEach(...) for every distinct value within
+                     * the column.
+                     */
+                    br.lines().collect(
+                            Collectors.groupingBy(str -> getCell(str, column),
+                                    toCollection(TreeSet::new)))
+                            .forEach((str, set) -> {
+                                System.out.println(str + ":");
+                                set.forEach(System.out::println);
+                            });
+                    break;
+                case "stat":
+                    verifyArgumentNumber(args, 3);
+
+                    /*
+                     * BufferedReader will be read several times.
+                     * Mark this point to return here after each pass.
+                     * BufferedReader will be read right after the headers line
+                     * because it is already read.
+                     */
+                    br.mark(READ_AHEAD_LIMIT);
+
+                    /*
+                     * Statistics can be collected by a custom collector in one
+                     * pass. One pass is preferable.
+                     */
+                    System.out.println(
+                            br.lines().collect(new Statistics(column)));
+
+                    /*
+                     * Alternatively, statistics can be collected
+                     * by a built-in API in several passes.
+                     * This method demonstrates how separate operations can be
+                     * implemented using a built-in API.
+                     */
+                    br.reset();
+                    statInSeveralPasses(br, column);
+                    break;
+                default:
+                    printUsageAndExit("Illegal argument" + args[0]);
+            }
+        } catch (IOException e) {
+            printUsageAndExit(e.toString());
+        }
+    }
+
+    private static void statInSeveralPasses(BufferedReader br, int column)
+            throws IOException {
+        System.out.println("#-----Statistics in several passes-------#");
+        //Create a comparator to compare records by the column.
+        Comparator<String> comparator
+                = Comparator.comparing(
+                        (String str) -> parseDouble(getCell(str, column)));
+        //Find max record by using Collectors.maxBy(...)
+        System.out.println(
+                "Max: " + br.lines().collect(maxBy(comparator)).get());
+        br.reset();
+        //Find min record by using Collectors.minBy(...)
+        System.out.println(
+                "Min: " + br.lines().collect(minBy(comparator)).get());
+        br.reset();
+        //Compute the average value and sum with
+        //Collectors.toDoubleSummaryStatistics(...)
+        DoubleSummaryStatistics doubleSummaryStatistics
+                = br.lines().collect(summarizingDouble(
+                    str -> parseDouble(getCell(str, column))));
+        System.out.println("Average: " + doubleSummaryStatistics.getAverage());
+        System.out.println("Sum: " + doubleSummaryStatistics.getSum());
+    }
+
+    private static void verifyArgumentNumber(String[] args, int n) {
+        if (args.length != n) {
+            printUsageAndExit("Expected " + n + " arguments but was "
+                    + args.length);
+        }
+    }
+
+    private static int getColumnNumber(List<String> header, String name) {
+        int column = header.indexOf(name);
+        if (column == -1) {
+            printUsageAndExit("There is no column with name " + name);
+        }
+        return column;
+    }
+
+    private static String getCell(String record, int column) {
+        return record.split(",")[column].trim();
+    }
+
+    private static void printUsageAndExit(String... str) {
+        System.out.println("Usages:");
+
+        System.out.println("CSVProcessor sort COLUMN_NAME ASC|DESC FILE");
+        System.out.println("Sort lines by column COLUMN_NAME in CSV FILE\n");
+
+        System.out.println("CSVProcessor search COLUMN_NAME REGEX FILE");
+        System.out.println("Search for REGEX in column COLUMN_NAME in CSV FILE\n");
+
+        System.out.println("CSVProcessor groupby COLUMN_NAME FILE");
+        System.out.println("Split lines into different groups according to column "
+                + "COLUMN_NAME value\n");
+
+        System.out.println("CSVProcessor stat COLUMN_NAME FILE");
+        System.out.println("Compute max/min/average/sum  statistics by column "
+                + "COLUMN_NAME\n");
+
+        Arrays.asList(str).forEach(System.err::println);
+        System.exit(1);
+    }
+
+    /*
+     * This is a custom implementation of the Collector interface.
+     * Statistics are objects gather max,min,sum,average statistics.
+     */
+    private static class Statistics
+            implements Collector<String, Statistics, Statistics> {
+
+
+        /*
+         * This implementation does not need to be thread safe because
+         * the parallel implementation of
+         * {@link java.util.stream.Stream#collect Stream.collect()}
+         * provides the necessary partitioning and isolation for safe parallel
+         * execution.
+         */
+        private String maxRecord;
+        private String minRecord;
+
+        private double sum;
+        private int lineCount;
+        private final BinaryOperator<String> maxOperator;
+        private final BinaryOperator<String> minOperator;
+        private final int column;
+
+        public Statistics(int column) {
+            this.column = column;
+            Comparator<String> cmp = Comparator.comparing(
+                    (String str) -> parseDouble(getCell(str, column)));
+            maxOperator = BinaryOperator.maxBy(cmp);
+            minOperator = BinaryOperator.minBy(cmp);
+        }
+
+        /*
+         * Process line.
+         */
+        public Statistics accept(String line) {
+            maxRecord = maxRecord == null
+                    ? line : maxOperator.apply(maxRecord, line);
+            minRecord = minRecord == null
+                    ? line : minOperator.apply(minRecord, line);
+
+            sum += parseDouble(getCell(line, column));
+            lineCount++;
+            return this;
+        }
+
+
+        /*
+         * Merge two Statistics.
+         */
+        public Statistics combine(Statistics stat) {
+            maxRecord = maxOperator.apply(maxRecord, stat.getMaxRecord());
+            minRecord = minOperator.apply(minRecord, stat.getMinRecord());
+            sum += stat.getSum();
+            lineCount += stat.getLineCount();
+            return this;
+        }
+
+        @Override
+        public String toString() {
+            StringBuilder sb = new StringBuilder();
+            sb.append("#------Statistics------#\n");
+            sb.append("Max: ").append(getMaxRecord()).append("\n");
+            sb.append("Min: ").append(getMinRecord()).append("\n");
+            sb.append("Sum = ").append(getSum()).append("\n");
+            sb.append("Average = ").append(average()).append("\n");
+            sb.append("#------Statistics------#\n");
+            return sb.toString();
+        }
+
+        @Override
+        public Supplier<Statistics> supplier() {
+            return () -> new Statistics(column);
+        }
+
+        @Override
+        public BiConsumer<Statistics, String> accumulator() {
+            return Statistics::accept;
+        }
+
+        @Override
+        public BinaryOperator<Statistics> combiner() {
+            return Statistics::combine;
+
+        }
+
+        @Override
+        public Function<Statistics, Statistics> finisher() {
+            return stat -> stat;
+        }
+
+        @Override
+        public Set<Characteristics> characteristics() {
+            return EnumSet.of(Characteristics.IDENTITY_FINISH);
+        }
+
+        private String getMaxRecord() {
+            return maxRecord;
+        }
+
+        private String getMinRecord() {
+            return minRecord;
+        }
+
+        private double getSum() {
+            return sum;
+        }
+
+        private double average() {
+            return sum / lineCount;
+        }
+
+        private int getLineCount() {
+            return lineCount;
+        }
+
+    }
+
+}