135 lines
3.0 KiB
Java
135 lines
3.0 KiB
Java
// collectiontopics/CollectionMethods.java
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// (c)2021 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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// Things you can do with all Collections
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import java.util.*;
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import static onjava.HTMLColors.*;
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public class CollectionMethods {
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public static void main(String[] args) {
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Collection<String> c =
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new ArrayList<>(LIST.subList(0, 4));
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c.add("ten");
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c.add("eleven");
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show(c);
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border();
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// Make an array from the List:
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Object[] array = c.toArray();
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// Make a String array from the List:
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String[] str = c.toArray(new String[0]);
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// Find max and min elements; this means
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// different things depending on the way
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// the Comparable interface is implemented:
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System.out.println(
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"Collections.max(c) = " + Collections.max(c));
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System.out.println(
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"Collections.min(c) = " + Collections.min(c));
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border();
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// Add a Collection to another Collection
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Collection<String> c2 =
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new ArrayList<>(LIST.subList(10, 14));
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c.addAll(c2);
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show(c);
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border();
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c.remove(LIST.get(0));
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show(c);
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border();
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// Remove all components that are
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// in the argument collection:
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c.removeAll(c2);
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show(c);
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border();
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c.addAll(c2);
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show(c);
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border();
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// Is an element in this Collection?
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String val = LIST.get(3);
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System.out.println(
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"c.contains(" + val + ") = " + c.contains(val));
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// Is a Collection in this Collection?
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System.out.println(
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"c.containsAll(c2) = " + c.containsAll(c2));
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Collection<String> c3 =
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((List<String>)c).subList(3, 5);
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// Keep all the elements that are in both
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// c2 and c3 (an intersection of sets):
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c2.retainAll(c3);
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show(c2);
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// Discard all c2 elements that also appear in c3:
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c2.removeAll(c3);
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System.out.println(
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"c2.isEmpty() = " + c2.isEmpty());
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border();
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// Functional operation:
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c = new ArrayList<>(LIST);
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c.removeIf(s -> !s.startsWith("P"));
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c.removeIf(s -> s.startsWith("Pale"));
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// Stream operation:
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c.stream().forEach(System.out::println);
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c.clear(); // Remove all elements
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System.out.println("after c.clear():" + c);
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}
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}
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/* Output:
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AliceBlue
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AntiqueWhite
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Aquamarine
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Azure
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ten
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eleven
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******************************
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Collections.max(c) = ten
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Collections.min(c) = AliceBlue
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******************************
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AliceBlue
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AntiqueWhite
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Aquamarine
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Azure
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ten
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eleven
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Brown
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BurlyWood
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CadetBlue
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Chartreuse
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******************************
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AntiqueWhite
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Aquamarine
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Azure
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ten
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eleven
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Brown
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BurlyWood
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CadetBlue
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Chartreuse
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******************************
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AntiqueWhite
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Aquamarine
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Azure
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ten
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eleven
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******************************
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AntiqueWhite
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Aquamarine
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Azure
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ten
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eleven
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Brown
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BurlyWood
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CadetBlue
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Chartreuse
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******************************
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c.contains(Azure) = true
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c.containsAll(c2) = true
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c2.isEmpty() = true
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******************************
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PapayaWhip
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PeachPuff
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Peru
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Pink
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Plum
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PowderBlue
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Purple
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after c.clear():[]
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*/
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