StreamArrayListProcessing.java
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/*
* A program to perform some basic operations on a list of Strings using Java streams
*/
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, Camllie");
names.add("Picasso, Pablo");
names.add("Gallen-Kallela, Akseli");
names.add("Zotto, Osvaldo");
names.add("Aung, KoKo");
names.add("Kyaw-Aung, Khant");
// 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> firstNameList = names.stream().map(n -> firstName(n)).collect(Collectors.toList());
System.out.print("First names: ");
for (String firstName : firstNameList) {
System.out.print(firstName + " ");
}
System.out.println();
// POINT C: Use map and the joining collector to created a String of just the first names of the names ArrayList
// with each name 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.
List<String> lastNameList = names.stream().map(n -> lastName(n)).collect(Collectors.toList());
System.out.print("Last names: ");
for (String lastName : lastNameList) {
System.out.print(lastName + " ");
}
System.out.println();
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("HyphenatedLastNames: " + 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 total length of all first names in the names ArrayList.
int firstNameTotalLength = firstNameList.stream().map(n -> n.length()).reduce(0,(n1, n2) -> n1 + n2);
System.out.println("Total first names length: " + firstNameTotalLength);
// POINT I: Print the integer value of the product of the length of all first names in the names ArrayList.
int namesProductLength = firstNameList.stream().map(n -> n.length()).reduce(1,(n1,n2) -> n1*n2);
System.out.println("Total product of names length: " + namesProductLength);
}
private static String lastName(String directoryStyleName) {
int lastNameComma = directoryStyleName.indexOf(",");
String lastName = directoryStyleName.substring(0,lastNameComma);
return lastName;
}
private static String firstName(String directoryStyleName) {
int firstNameComma = directoryStyleName.indexOf(",");
String firstName = directoryStyleName.substring(firstNameComma+2);
return firstName;
}
}