Lists
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import java.util.ArrayList; import java.util.Arrays; import java.util.List; import org.pureprogrammer.Utils; public class Lists1 { public static void main(String[] args) { final int NUM_SQUARES = 5; List<Integer> squares = new ArrayList<>(); // Put the squares into the list for (int i = 0; i < NUM_SQUARES; ++i) { squares.add(i * i); } // Print out the squares from the list for (int i = 0; i < squares.size(); ++i) { System.out.println(Utils.format("{0:d}^2 = {1:d}", i, squares.get(i))); } System.out.println(Utils.listToString(squares)); } }
Output
$ javac -Xlint Lists1.java
$ java -ea Lists1
0^2 = 0
1^2 = 1
2^2 = 4
3^2 = 9
4^2 = 16
[0, 1, 4, 9, 16]
import java.util.ArrayList; import java.util.Arrays; import java.util.List; import org.pureprogrammer.Utils; public class Lists2 { public static void main(String[] args) { List<Integer> squares = Utils.listFromIntegers(new int[]{0, 1, 4, 9, 16, 25}); // Print out the squares from the list for (int i = 0; i < squares.size(); ++i) { System.out.println(Utils.format("{0:d}^2 = {1:d}", i, squares.get(i))); } } }
Output
$ javac -Xlint Lists2.java
$ java -ea Lists2
0^2 = 0
1^2 = 1
2^2 = 4
3^2 = 9
4^2 = 16
5^2 = 25
import java.util.ArrayList; import java.util.Arrays; import java.util.List; import org.pureprogrammer.Utils; public class Lists3 { public static void main(String[] args) { List<String> names = Utils.listFromStrings(new String[]{"Fred", "Wilma", "Barney", "Betty"}); for (String name : names) { System.out.println("Hello, " + name + "!"); } names = Arrays.asList("Harry", "Ron", "Hermione"); for (String name : names) { System.out.println("Hello, " + name + "!"); } } }
Output
$ javac -Xlint Lists3.java
$ java -ea Lists3
Hello, Fred!
Hello, Wilma!
Hello, Barney!
Hello, Betty!
Hello, Harry!
Hello, Ron!
Hello, Hermione!
import org.pureprogrammer.Utils; public class Lists4 { public static void main(String[] args) { // Print out the command line arguments for (int i = 1; i <= args.length; ++i) { System.out.println(i + ":" + args[i - 1]); } } }
Output
$ javac -Xlint Lists4.java
$ java -ea Lists4 Fred Barney Wilma Betty
1:Fred
2:Barney
3:Wilma
4:Betty
$ javac -Xlint Lists4.java
$ java -ea Lists4 10 20 30 40
1:10
2:20
3:30
4:40
import java.util.ArrayList; import java.util.Arrays; import java.util.List; import org.pureprogrammer.Utils; public class Lists5 { public static void main(String[] args) { List<String> names = Utils.listFromStrings(new String[]{"Fred", "Wilma", "Barney", "Betty"}); // Print out the name based on command line argument 1-4 for (int i = 1; i <= args.length; ++i) { final int x = Utils.stoiWithDefault(args[i - 1], 0); System.out.println(i + ":" + names.get(x - 1)); } } }
Output
$ javac -Xlint Lists5.java
$ java -ea Lists5 1 2 3 4
1:Fred
2:Wilma
3:Barney
4:Betty
$ javac -Xlint Lists5.java
$ java -ea Lists5 4 3 2 1
1:Betty
2:Barney
3:Wilma
4:Fred
$ javac -Xlint Lists5.java
$ java -ea Lists5 1 3
1:Fred
2:Barney
Questions
- {{Who's on first?}}
- {{Who's on second?}}
- {{Who's on third?}}
Projects
More ★'s indicate higher difficulty level.
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References
- [[Java Language Specification]], Java SE 17 Edition, Gosling, et. al., 2021.
- [[Java Tutorials]]
- [[Java at TutorialsPoint]]
- Download Java at [[Amazon Corretto]], [[Azul Zulu]], [[Eclipse Temurin]] or [[Oracle JDK]]