StreamArrayListProcessing.java
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package arraylists;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
public class StreamArrayListProcessing {
public static void main(String[] args) {
// POINT A: Add some strings which represent names to an ArrayList.
List<String> names = new ArrayList<>();
names.add("Holiday, Billie");
names.add("Claudel, Camille");
names.add("Picasso, Pablo");
names.add("Gallen-Kallela, Akseli");
names.add("Zotto, Osvaldo");
names.add("Eugen, Prinz");
names.add("Hipper, Admiral");
names.add("HMS, Amazon");
// POINT B: Use map and the toList collector to create an ArrayList of just the first names of the names ArrayList.
// Use a for loop to print out the names. separated by spaces.
List<String> firstNamesList = names.stream()
.map(n -> firstName(n))
.collect(Collectors.toList());
System.out.print("First names: ");
for (String firstName : firstNamesList) {
System.out.print(firstName + " ");
}
System.out.println();
// POINT C: Use map and the joining collector to create a String of just the first names of the names ArrayList
// with each names separated by a comma. Print it.
String firstNames = names.stream()
.map(n -> firstName(n))
.collect(Collectors.joining(", "));
System.out.println("First names: " + firstNames);
// POINT D: By analogy from point C, print a comma-separated list of the last names in the names ArrayList.
String lastNames = names.stream()
.map(n -> lastName(n))
.collect(Collectors.joining(", "));
System.out.println("Last names: " + lastNames);
// POINT E: Print a comma-separated list of all uppercase first names from the list of names in the names ArrayList.
String upperCaseFirstNames = names.stream()
.map(n -> firstName(n))
.map(n -> n.toUpperCase())
.collect(Collectors.joining(", "));
System.out.println("Uppercase first names: " + upperCaseFirstNames);
// POINT F: Print a comma-separated list of all hyphenated last names from the list of names in the names ArrayList.
String hyphenatedLastNames = names.stream()
.map(n -> lastName(n))
.filter(n -> n.contains("-"))
.collect(Collectors.joining(", "));
System.out.println("Hyphenated last names: " + hyphenatedLastNames);
// POINT G: Print the integer value of the total length of all names in the names ArrayList.
int totalLength = names.stream()
.map(n -> n.length())
.reduce(0, (n1, n2) -> n1 + n2);
System.out.println("Total length: " + totalLength);
// POINT H: Print the integer value of the product of the length of all first names in the names ArrayList.
int firstLength = names.stream()
.map(n -> firstName(n).length())
.reduce(0, (n1, n2) -> n1 + n2);
System.out.println("First name total length: " + firstLength);
// POINT I: Print the integer value of the product of the length of all first names in the names ArrayList.
int productLength = names.stream()
.map(n -> n.length())
.reduce(1, (n1,n2) -> n1 * n2);
System.out.println("Product of the lengths of the names: " + productLength);
}
private static String firstName(String directoryStyleName) {
int firstNamePosition = directoryStyleName.indexOf(",");
String firstName = directoryStyleName.substring(firstNamePosition + 2, directoryStyleName.length());
return firstName;
}
private static String lastName(String directoryStyleName) {
int lastNamePosition = directoryStyleName.indexOf(",");
String lastName = directoryStyleName.substring(0, lastNamePosition);
return lastName;
}
}