|
StreamArrayListProcessing.java
|
1
2
3 /*
4 * A program to perform some basic operations on a list of Strings using Java streams3 */
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, Camllie");
19 names.add("Picasso, Pablo");
20 names.add("Gallen-Kallela, Akseli");
21 names.add("Zotto, Osvaldo");
22 names.add("Bob, BobBy");
23 names.add("Jadwin-Gavin, Adam");
24 // POINT B: Use map and the toList collector to create an ArrayList of just the first names of the names ArrayList.
25 // Use a for loop to print out the names, separated by spaces.
26 List<String> firstNameList = names.stream().map(n -> firstName(n)).collect(Collectors.toList());
27 System.out.print("First names: ");
28 for (String firstName : firstNameList) {
29 System.out.print(firstName + " ");
30 }
31 System.out.println();
32 // POINT C: Use map and the joining collector to created a String of just the first names of the names ArrayList
33 // with each name separated by a comma. Print it.
34 String firstNames = names.stream().map(n -> firstName(n)).collect(Collectors.joining(", "));
35 System.out.println("First names: " + firstNames);
36 // POINT D: By analogy from point C, print a comma-separated list of the last names in the names ArrayList.
37 List<String> lastNameList = names.stream().map(n -> lastName(n)).collect(Collectors.toList());
38 System.out.print("Last names: ");
39 for (String lastName : lastNameList) {
40 System.out.print(lastName + " ");
41 }
42 System.out.println();
43 String lastNames = names.stream().map(n -> lastName(n)).collect(Collectors.joining(", "));
44 System.out.println("Last names: " + lastNames);
45 // POINT E: Print a comma-separated list of all uppercase first names from the list of names in the names ArrayList.
46 String upperCaseFirstNames = names.stream().map(n -> firstName(n)).map(n -> n.toUpperCase()).collect(Collectors.joining(", "));
47 System.out.println("Uppercase first names: " + upperCaseFirstNames);
48 // POINT F: Print a comma-separated list of all hyphenated last names from the list of names in the names ArrayList.
49 String hyphenatedLastNames = names.stream().map(n -> lastName(n)).filter(n -> n.contains("-")).collect(Collectors.joining(", "));
50 System.out.println("HyphenatedLastNames: " + hyphenatedLastNames);
51 // POINT G: Print the integer value of the total length of all names in the names ArrayList.
52 int totalLength = names.stream().map(n -> n.length()).reduce(0,(n1,n2) -> n1 + n2);
53 System.out.println("Total Length: " + totalLength);
54 // POINT H: Print the integer value of the total length of all first names in the names ArrayList.
55 int firstNameTotalLength = firstNameList.stream().map(n -> n.length()).reduce(0,(n1, n2) -> n1 + n2);
56 System.out.println("Total first names length: " + firstNameTotalLength);
57 // POINT I: Print the integer value of the product of the length of all first names in the names ArrayList.
58 int namesProductLength = firstNameList.stream().map(n -> n.length()).reduce(1,(n1,n2) -> n1*n2);
59 System.out.println("Total product of names length: " + namesProductLength);
60 }
61 private static String lastName(String directoryStyleName) {
62 int lastNameComma = directoryStyleName.indexOf(",");
63 String lastName = directoryStyleName.substring(0,lastNameComma);
64 return lastName;
65 }
66 private static String firstName(String directoryStyleName) {
67 int firstNameComma = directoryStyleName.indexOf(",");
68 String firstName = directoryStyleName.substring(firstNameComma+2);
69 return firstName;
70 }
71
72 }
73
74