1    /* 
2     * A program to perform some basic operations on a list of Strings 
3     * using Java streams. 
4     */
5    
6    package arraylists;
7    
8    import java.util.ArrayList;
9    import java.util.List;
10   import java.util.stream.Collectors;
11   
12   public class StreamArrayListProcessing {
13   
14       public static void main(String[] args) {
15           // POINT A: Add some strings which represent names to an ArrayList. List<String> names = new ArrayList<>();
16           List<String> names = new ArrayList<>();
17           names.add("Holiday, Billie");
18           names.add("Claudel, Camille");
19           names.add("Picasso, Pablo");
20           names.add("Gallen-Kallela, Akseli");
21           names.add("Zotto, Osvaldo");
22   
23           // POINT B: Use map and the toList collector to create an ArrayList of just
24           //          the first names of the names ArrayList. Use a for loop to print
25           // out the names, separated by spaces.
26   
27           List<String> firstNamesList = names.stream().map(n -> firstName(n)).collect(Collectors.toList());
28           System.out.print("First names: ");
29           for (String firstName : firstNamesList) {
30               System.out.print(firstName + " ");
31           }
32           System.out.println();
33   
34           // POINT C: Use map and the joining collector to create a String of just
35           //          the first names of the names ArrayList with each name seperated
36           //          by a coma. Print it.
37   
38           String firstNames = names.stream()
39                   .map(n -> firstName(n))
40                   .collect(Collectors.joining(", "));
41   
42           System.out.println("First names: " + firstNames);
43   
44           // POINT D: By analogy from point C, print a coma-seperated list of the
45           //          last names in the names ArrayList
46   
47           String lastNames = names.stream()
48                   .map(n -> lastName(n))
49                   .collect(Collectors.joining(", "));
50   
51           System.out.println("Last names: " + lastNames);
52   
53           // POINT E: Print a coma-seperated list of all uppercase first names
54           //          from the list of names in the names ArrayList
55   
56           String upperCaseFirstNames = names.stream()
57                   .map(n -> firstName(n))
58                   .map(n -> n.toUpperCase())
59                   .collect(Collectors.joining(", "));
60   
61           System.out.println("Uppercase first names: " + upperCaseFirstNames);
62   
63           // POINT F: Print a coma-seperated list of all hyphenated last names
64           //          from the list of names in the names ArrayList
65   
66           String hyphenatedLastNames = names.stream()
67                   .map(n -> lastName(n))
68                   .filter(n -> n.contains("-"))
69                   .collect(Collectors.joining(", "));
70   
71           System.out.println("hypenated last names: " + hyphenatedLastNames);
72   
73           // POINT G: Print the integer value of the total length of all names
74           //          in the names ArrayList.
75   
76           int totalLength = names.stream()
77                   .map(n -> n.length())
78                   .reduce(0, (n1, n2) -> n1 + n2);
79           System.out.println("Total length: " + totalLength);
80   
81           // POINT H: Print the integer value of the total length of all
82           //          first names in the names ArrayList.
83   
84           int totalFirstLength = firstNamesList.stream()
85                   .map(n -> n.length())
86                   .reduce(0, (n1, n2) -> n1 + n2);
87           System.out.println("Total first names length:" + totalFirstLength);
88   
89   
90           // POINT I: Print the integer value of the product of the length of
91           //          all first names in the names ArrayList.
92   
93           int totalProduct = names.stream()
94                   .map(n -> n.length())
95                   .reduce(1, (n1, n2) -> n1 + n2);
96           System.out.println("Total product: " + totalProduct);
97       }
98   
99       private static String firstName(String directoryStyleName) {
100          int p1 = directoryStyleName.indexOf(" ");
101          return directoryStyleName.substring(p1 + 1);
102      }
103  
104      private static String lastName(String directoryStyleName) {
105          int p1 = directoryStyleName.indexOf(",");
106          return directoryStyleName.substring(0, p1);
107      }
108  
109  
110  }