StreamArrayListProcessing.java
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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.
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 names.add("Eugen, Prinz");
24 names.add("Hipper, Admiral");
25 names.add("HMS, Amazon");
26
27 // POINT B: Use map and the toList collector to create an ArrayList of just the first names of the names ArrayList.
28 // Use a for loop to print out the names. separated by spaces.
29 List<String> firstNamesList = names.stream()
30 .map(n -> firstName(n))
31 .collect(Collectors.toList());
32
33 System.out.print("First names: ");
34 for (String firstName : firstNamesList) {
35 System.out.print(firstName + " ");
36 }
37 System.out.println();
38
39 // POINT C: Use map and the joining collector to create a String of just the first names of the names ArrayList
40 // with each names separated by a comma. Print it.
41 String firstNames = names.stream()
42 .map(n -> firstName(n))
43 .collect(Collectors.joining(", "));
44
45 System.out.println("First names: " + firstNames);
46
47 // POINT D: By analogy from point C, print a comma-separated list of the last names in the names ArrayList.
48 String lastNames = names.stream()
49 .map(n -> lastName(n))
50 .collect(Collectors.joining(", "));
51
52 System.out.println("Last names: " + lastNames);
53
54 // POINT E: Print a comma-separated list of all uppercase first names from the list of names in the names ArrayList.
55 String upperCaseFirstNames = names.stream()
56 .map(n -> firstName(n))
57 .map(n -> n.toUpperCase())
58 .collect(Collectors.joining(", "));
59
60 System.out.println("Uppercase first names: " + upperCaseFirstNames);
61
62 // POINT F: Print a comma-separated list of all hyphenated last names from the list of names in the names ArrayList.
63 String hyphenatedLastNames = names.stream()
64 .map(n -> lastName(n))
65 .filter(n -> n.contains("-"))
66 .collect(Collectors.joining(", "));
67
68 System.out.println("Hyphenated last names: " + hyphenatedLastNames);
69
70 // POINT G: Print the integer value of the total length of all names in the names ArrayList.
71 int totalLength = names.stream()
72 .map(n -> n.length())
73 .reduce(0, (n1, n2) -> n1 + n2);
74
75 System.out.println("Total length: " + totalLength);
76
77 // POINT H: Print the integer value of the product of the length of all first names in the names ArrayList.
78 int firstLength = names.stream()
79 .map(n -> firstName(n).length())
80 .reduce(0, (n1, n2) -> n1 + n2);
81
82 System.out.println("First name total length: " + firstLength);
83
84 // POINT I: Print the integer value of the product of the length of all first names in the names ArrayList.
85 int productLength = names.stream()
86 .map(n -> n.length())
87 .reduce(1, (n1,n2) -> n1 * n2);
88
89 System.out.println("Product of the lengths of the names: " + productLength);
90
91 }
92
93 private static String firstName(String directoryStyleName) {
94 int firstNamePosition = directoryStyleName.indexOf(",");
95 String firstName = directoryStyleName.substring(firstNamePosition + 2, directoryStyleName.length());
96 return firstName;
97 }
98
99 private static String lastName(String directoryStyleName) {
100 int lastNamePosition = directoryStyleName.indexOf(",");
101 String lastName = directoryStyleName.substring(0, lastNamePosition);
102 return lastName;
103 }
104 }