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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 names.add("Sumner, Elijah");
23 names.add("DePretis, Amy");
24
25 //POINT B: Use map and the toList collector to create an ArrayList of just
26 // the first names of the names ArrayList. Use a for loop to print
27 // out the names, separated by spaces.
28
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 a map and the joining collector to create a String of just
40 // the first names of the names ArrayList with each name separated
41 // by a comma. Print it.
42
43 String firstNames = names.stream()
44 .map(n -> firstName(n))
45 .collect(Collectors.joining(", "));
46
47 System.out.println("First names: " + firstNames);
48
49 //POINT D: By analogy from point C, print a comma-separated list of the
50 // last names in the names ArrayList.
51
52 String lastNames = names.stream()
53 .map(n -> lastName(n))
54 .collect(Collectors.joining(", "));
55 System.out.println("Last names: " + lastNames);
56
57 //POINT E: Print a comma-separated list of all uppercase first names
58 // from the list of names in the names ArrayList.
59
60 String upperCaseFirstNames = names.stream()
61 .map(n -> firstName(n))
62 .map(n -> n.toUpperCase())
63 .collect(Collectors.joining(", "));
64
65 System.out.println("Uppercase first names: " + upperCaseFirstNames);
66
67 //POINT F: Print a comma-separated list of all hyphenated last names
68 // from the list of names in the names ArrayList.
69
70 String hyphenatedLastNames = names.stream()
71 .map(n -> lastName(n))
72 .filter(n -> n.contains("-"))
73 .collect(Collectors.joining(", "));
74
75 System.out.println("Hyphenated last names: " + hyphenatedLastNames);
76
77 //POINT G: Print the integer value of the total length of all names
78 // in the names ArrayList.
79
80 int totalLength = names.stream()
81 .map(n -> n.length())
82 .reduce(0, (n1, n2) -> n1 + n2);
83
84 System.out.println("Total length: " + totalLength);
85
86 //POINT H: Print the integer value of the total length of all
87 // first names in the names ArrayList.
88
89 int firstNameLength = names.stream()
90 .map(n -> firstName(n))
91 .map(n -> n.length())
92 .reduce(0, (n1, n2) -> n1 + n2);
93
94 System.out.println("First name length: " + firstNameLength);
95
96 //POINT I: Print the integer value of the product of the length of
97 // all first names in the names ArrayList.
98
99 int lastNameLength = names.stream()
100 .map(n -> lastName(n))
101 .map(n -> n.length())
102 .reduce(0, (n1, n2) -> n1 + n2);
103
104 System.out.println("Last name length: " + lastNameLength);
105 }
106
107 private static String firstName(String directoryStyleName) {
108 int commaPosition = directoryStyleName.indexOf(",");
109 String firstName = directoryStyleName.substring(commaPosition+2);
110 return firstName;
111 }
112
113 private static String lastName(String directoryStyleName) {
114 int commaPosition = directoryStyleName.indexOf(",");
115 String lastName = directoryStyleName.substring(0,commaPosition);
116 return lastName;
117 }
118 }
119