Pre-compile regex pattern and use splitAsStream.

LambdaLab/test/exercises/E_IntermediateStreams.java

@@ -9,6 +9,7 @@ import java.util.Arrays;
 import java.util.Comparator;
 import java.util.List;
 import java.util.concurrent.atomic.LongAdder;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -51,8 +52,10 @@ public class E_IntermediateStreams {
 
     /**
      * Collect all the words from the text file into a list.
-     * Use String.split(REGEXP) to split a string into words.
-     * REGEXP is defined at the bottom of this file.
+     * Use the regular expression pattern WORD_PATTERN to split
+     * a string into words, and use Pattern.splitAsStream(String)
+     * to do the splitting. WORD_PATTERN is defined at the bottom
+     * of this file.
      *
      * @throws IOException
      */
@@ -194,7 +197,8 @@ public class E_IntermediateStreams {
 // ========================================================
 
 
-    static final String REGEXP = "[- .:,]+"; // for splitting into words
+    // Pattern for splitting a string into words
+    static final Pattern WORD_PATTERN = Pattern.compile("[- .:,]+");
 
     private BufferedReader reader;
 

LambdaLab/test/exercises/F_AdvancedStreams.java

@@ -17,6 +17,7 @@ import java.util.IntSummaryStatistics;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
@@ -241,7 +242,8 @@ public class F_AdvancedStreams {
 // ========================================================
 
 
-    static final String REGEXP = "[- .:,]+"; // for splitting into words
+    // Pattern for splitting a string into words
+    static final Pattern WORD_PATTERN = Pattern.compile("[- .:,]+");
 
     private BufferedReader reader;
 

LambdaLab/test/solutions/E_IntermediateStreams.java

@@ -9,6 +9,7 @@ import java.util.Arrays;
 import java.util.Comparator;
 import java.util.List;
 import java.util.concurrent.atomic.LongAdder;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -57,8 +58,10 @@ public class E_IntermediateStreams {
 
     /**
      * Collect all the words from the text file into a list.
-     * Use String.split(REGEXP) to split a string into words.
-     * REGEXP is defined at the bottom of this file.
+     * Use the regular expression pattern WORD_PATTERN to split
+     * a string into words, and use Pattern.splitAsStream(String)
+     * to do the splitting. WORD_PATTERN is defined at the bottom
+     * of this file.
      *
      * @throws IOException
      */
@@ -68,7 +71,7 @@ public class E_IntermediateStreams {
         //BEGINREMOVE
         List<String> output =
             reader.lines()
-                  .flatMap(line -> Arrays.stream(line.split(REGEXP)))
+                  .flatMap(line -> WORD_PATTERN.splitAsStream(line))
                   .collect(Collectors.toList());
         // Alternatively, Stream.of() can be used instead of Arrays.stream().
         //ENDREMOVE
@@ -109,7 +112,7 @@ public class E_IntermediateStreams {
         //BEGINREMOVE
         List<String> output =
             reader.lines()
-                  .flatMap(line -> Stream.of(line.split(REGEXP)))
+                  .flatMap(line -> WORD_PATTERN.splitAsStream(line))
                   .filter(word -> word.length() >= 8)
                   .map(String::toLowerCase)
                   .sorted()
@@ -141,7 +144,7 @@ public class E_IntermediateStreams {
         //BEGINREMOVE
         List<String> result =
             reader.lines()
-                  .flatMap(line -> Stream.of(line.split(REGEXP)))
+                  .flatMap(line -> WORD_PATTERN.splitAsStream(line))
                   .filter(word -> word.length() >= 8)
                   .map(String::toLowerCase)
                   .sorted(Comparator.reverseOrder())
@@ -172,7 +175,7 @@ public class E_IntermediateStreams {
         //BEGINREMOVE
         List<String> result =
             reader.lines()
-                  .flatMap(line -> Stream.of(line.split(REGEXP)))
+                  .flatMap(line -> WORD_PATTERN.splitAsStream(line))
                   .map(String::toLowerCase)
                   .distinct()
                   .sorted(Comparator.comparingInt(String::length)
@@ -219,7 +222,7 @@ public class E_IntermediateStreams {
         LongAdder adder = new LongAdder();
         long distinctCount =
             reader.lines()
-                  .flatMap(line -> Stream.of(line.split(REGEXP)))
+                  .flatMap(line -> WORD_PATTERN.splitAsStream(line))
                   .map(String::toLowerCase)
                   .peek(s -> adder.increment())
                   .distinct()
@@ -246,7 +249,8 @@ public class E_IntermediateStreams {
 // ========================================================
 
 
-    static final String REGEXP = "[- .:,]+"; // for splitting into words
+    // Pattern for splitting a string into words
+    static final Pattern WORD_PATTERN = Pattern.compile("[- .:,]+");
 
     private BufferedReader reader;
 

LambdaLab/test/solutions/F_AdvancedStreams.java

@@ -17,6 +17,7 @@ import java.util.IntSummaryStatistics;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
@@ -70,7 +71,7 @@ public class F_AdvancedStreams {
         //BEGINREMOVE
         String result =
             reader.lines()
-                  .flatMap(line -> Arrays.stream(line.split(REGEXP)))
+                  .flatMap(line -> WORD_PATTERN.splitAsStream(line))
                   .reduce((a, b) -> b)
                   .get();
         //ENDREMOVE
@@ -97,7 +98,7 @@ public class F_AdvancedStreams {
         //BEGINREMOVE
         Map<Integer, List<String>> result =
             reader.lines()
-                  .flatMap(line -> Arrays.stream(line.split(REGEXP)))
+                  .flatMap(line -> WORD_PATTERN.splitAsStream(line))
                   .collect(Collectors.groupingBy(String::length));
         //ENDREMOVE
 
@@ -129,7 +130,7 @@ public class F_AdvancedStreams {
         //BEGINREMOVE
         Map<Integer, Long> result =
             reader.lines()
-                  .flatMap(line -> Arrays.stream(line.split(REGEXP)))
+                  .flatMap(line -> WORD_PATTERN.splitAsStream(line))
                   .collect(Collectors.groupingBy(String::length, Collectors.counting()));
         //ENDREMOVE
 
@@ -173,7 +174,7 @@ public class F_AdvancedStreams {
         //BEGINREMOVE
         Map<String, Long> result =
             reader.lines()
-                  .flatMap(line -> Stream.of(line.split(REGEXP)))
+                  .flatMap(line -> WORD_PATTERN.splitAsStream(line))
                   .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
                       // or use word -> word instead of Function.identity()
 
@@ -226,7 +227,7 @@ public class F_AdvancedStreams {
         //BEGINREMOVE
         Map<String, Map<Integer, List<String>>> result =
             reader.lines()
-                  .flatMap(line -> Stream.of(line.split(REGEXP)))
+                  .flatMap(line -> WORD_PATTERN.splitAsStream(line))
                   .collect(Collectors.groupingBy(word -> word.substring(0,1),
                                                  Collectors.groupingBy(String::length)));
         //ENDREMOVE
@@ -300,7 +301,8 @@ public class F_AdvancedStreams {
 // ========================================================
 
 
-    static final String REGEXP = "[- .:,]+"; // for splitting into words
+    // Pattern for splitting a string into words
+    static final Pattern WORD_PATTERN = Pattern.compile("[- .:,]+");
 
     private BufferedReader reader;
 

README.md

-* Balloon stuff -- a bit complicated, but useful to show constructor references
-* Maurice's forEach example List<StringBuilder>
-* reorganize files:
-   C - default methods
-   D - simple streams and collectors
-   E - composite collectors
-   F - custom collectors
-   G - challenges
-   
-
 Java 8 Lambdas Hands-on Lab Materials
 
 (version for late 2016 conferences)