89 lines
2.9 KiB
Java
89 lines
2.9 KiB
Java
// containersindepth/CollectionMethods.java
|
|
// ©2016 MindView LLC: see Copyright.txt
|
|
// We make no guarantees that this code is fit for any purpose.
|
|
// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
|
|
// Things you can do with all Collections.
|
|
import java.util.*;
|
|
import onjava.*;
|
|
|
|
public class CollectionMethods {
|
|
public static void main(String[] args) {
|
|
Collection<String> c = new ArrayList<>();
|
|
c.addAll(Countries.names(6));
|
|
c.add("ten");
|
|
c.add("eleven");
|
|
System.out.println(c);
|
|
// Make an array from the List:
|
|
Object[] array = c.toArray();
|
|
// Make a String array from the List:
|
|
String[] str = c.toArray(new String[0]);
|
|
// Find max and min elements; this means
|
|
// different things depending on the way
|
|
// the Comparable interface is implemented:
|
|
System.out.println(
|
|
"Collections.max(c) = " + Collections.max(c));
|
|
System.out.println(
|
|
"Collections.min(c) = " + Collections.min(c));
|
|
// Add a Collection to another Collection
|
|
Collection<String> c2 = new ArrayList<>();
|
|
c2.addAll(Countries.names(6));
|
|
c.addAll(c2);
|
|
System.out.println(c);
|
|
c.remove(Countries.DATA[0][0]);
|
|
System.out.println(c);
|
|
c.remove(Countries.DATA[1][0]);
|
|
System.out.println(c);
|
|
// Remove all components that are
|
|
// in the argument collection:
|
|
c.removeAll(c2);
|
|
System.out.println(c);
|
|
c.addAll(c2);
|
|
System.out.println(c);
|
|
// Is an element in this Collection?
|
|
String val = Countries.DATA[3][0];
|
|
System.out.println(
|
|
"c.contains(" + val + ") = " + c.contains(val));
|
|
// Is a Collection in this Collection?
|
|
System.out.println(
|
|
"c.containsAll(c2) = " + c.containsAll(c2));
|
|
Collection<String> c3 =
|
|
((List<String>)c).subList(3, 5);
|
|
// Keep all the elements that are in both
|
|
// c2 and c3 (an intersection of sets):
|
|
c2.retainAll(c3);
|
|
System.out.println(c2);
|
|
// Throw away all the elements
|
|
// in c2 that also appear in c3:
|
|
c2.removeAll(c3);
|
|
System.out.println("c2.isEmpty() = " + c2.isEmpty());
|
|
c = new ArrayList<>();
|
|
c.addAll(Countries.names(6));
|
|
System.out.println(c);
|
|
c.clear(); // Remove all elements
|
|
System.out.println("after c.clear():" + c);
|
|
}
|
|
}
|
|
/* Output:
|
|
[ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI,
|
|
ten, eleven]
|
|
Collections.max(c) = ten
|
|
Collections.min(c) = ALGERIA
|
|
[ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI,
|
|
ten, eleven, ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA
|
|
FASO, BURUNDI]
|
|
[ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI, ten,
|
|
eleven, ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO,
|
|
BURUNDI]
|
|
[BENIN, BOTSWANA, BURKINA FASO, BURUNDI, ten, eleven,
|
|
ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI]
|
|
[ten, eleven]
|
|
[ten, eleven, ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA
|
|
FASO, BURUNDI]
|
|
c.contains(BOTSWANA) = true
|
|
c.containsAll(c2) = true
|
|
[ANGOLA, BENIN]
|
|
c2.isEmpty() = true
|
|
[ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI]
|
|
after c.clear():[]
|
|
*/
|