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StreamArrayListProcessing.java
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1 /*
2 * A program to perform some basic operations on a list of Strings using Java streams.
3 */
4 package arraylists;
5
6 import java.util.ArrayList;
7 import java.util.List;
8 import java.util.stream.Collectors;
9
10 public class StreamArrayListProcessing {
11
12 public static void main(String[] args){
13 //POINT A: Add some strings which represent names to an ArrayList.
14 List<String> names = new ArrayList<>();
15 names.add("Holiday, Billie");
16 names.add("Claudel, Camille");
17 names.add("Picasso, Pablo");
18 names.add("Gallen-Kallela, Akseli");
19 names.add("Zotto, Osvaldo");
20 names.add("Camacho III, Franklin");
21
22 //POINT B: Use map and the toList collector to create an Array List of just
23 // the first names of the names ArrayList. Use a for loop to print
24 // out the names, separated by spaces.
25
26 List<String> firstNamesList = names.stream()
27 .map(n -> firstName(n))
28 .collect(Collectors.toList());
29
30 System.out.print("First names: ");
31 for (String firstName : firstNamesList){
32 System.out.print(firstName + " ");
33 }
34 System.out.println();
35 //POINT C: Use map and the joining collector to create a String of just the first names
36 // of the names ArrayList with each name separated by a comma. 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 comma-separated list of the last names in the names ArrayList.
45
46 String lastNames = names.stream()
47 .map(n -> lastName(n))
48 .collect(Collectors.joining(", "));
49
50 System.out.println("Last names: " + lastNames);
51
52 //POINT E: Print a comma-separated list of all uppercase first names from the list of names in the names ArrayList.
53
54 String upperCaseFirstNames = names.stream()
55 .map(n -> firstName(n))
56 .map(n -> n.toUpperCase())
57 .collect(Collectors.joining(", "));
58
59 System.out.println("Uppercase first names: " + upperCaseFirstNames);
60
61 //POINT F: Print a comma-separated list of all hyphenated last names from the list of names in the names ArrayList.
62
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
72 int totalLength = names.stream()
73 .map(n -> n.length())
74 .reduce(0, (n1, n2) -> n1 + n2);
75
76 System.out.println("Total length: " + totalLength);
77
78 //POINT H: Print the integer value of the total length of all first names in the names ArrayList.
79
80 int totalLengthOfFirstNames = names.stream()
81 .map(n -> firstName(n))
82 .map(n -> n.length())
83 .reduce(0, (n1, n2) -> n1 + n2);
84
85 System.out.println("Total length of first names: " + totalLengthOfFirstNames);
86
87 //POINT I: Print the integer value of the product of the length of all first names in the names ArrayList.
88
89 int totalProductOfFirstNames = names.stream()
90 .map(n -> firstName(n))
91 .map(n -> n.length())
92 .reduce(1, (n1, n2) -> n1 * n2);
93
94 System.out.println("Total product of first names: " + totalProductOfFirstNames);
95 }
96
97 private static String firstName(String directoryStyleName) {
98 int dsnCommaPosition = directoryStyleName.indexOf(",");
99 String firstName = directoryStyleName.substring(dsnCommaPosition + 2);
100 return firstName;
101 }
102 private static List<String> firstNames(List<String> names) {
103 List<String> firsts = new ArrayList<>();
104 for (String name :names) {
105 firsts.add(firstName(name));
106 }
107 return firsts;
108 }
109 private static String lastName(String directoryStyleName) {
110
111 int dsnCommaPosition = directoryStyleName.indexOf(",");
112 String lastName = directoryStyleName.substring(0, dsnCommaPosition);
113 return lastName;
114 }
115 private static List<String> lastNames(List<String> names) {
116 List<String> lasts = new ArrayList<>();
117 for (String name :names) {
118 lasts.add(lastName(name));
119 }
120 return lasts;
121 }
122 public static List<String> upperCaseNames(List<String> names) {
123 List<String> uppercases = new ArrayList<>();
124 for (String name : names) {
125 uppercases.add(name.toUpperCase());
126 }
127 return uppercases;
128 }
129 public static List<String> hyphenatedNames(List<String> names) {
130 List<String> hyphenateds = new ArrayList<>();
131 for (String name : names) {
132 if (name.contains("-")) {
133 hyphenateds.add(name);
134 }
135 }
136 return hyphenateds;
137 }
138 public static int totalNameLength(List<String> names) {
139 int totalLength = 0;
140 for (String name : names) {
141 totalLength = totalLength + name.length();
142 }
143 return totalLength;
144 }
145 public static int totalNameProduct(List<String> names) {
146 int totalProduct = 1;
147 for (String name : names) {
148 totalProduct = totalProduct * name.length();
149 }
150 return totalProduct;
151 }
152
153 }
154
155