75 lines
2.6 KiB
Java
75 lines
2.6 KiB
Java
//: containers/CollectionMethods.java
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// Things you can do with all Collections.
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import java.util.*;
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import net.mindview.util.*;
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import static net.mindview.util.Print.*;
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public class CollectionMethods {
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public static void main(String[] args) {
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Collection<String> c = new ArrayList<>();
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c.addAll(Countries.names(6));
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c.add("ten");
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c.add("eleven");
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print(c);
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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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print("Collections.max(c) = " + Collections.max(c));
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print("Collections.min(c) = " + Collections.min(c));
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// Add a Collection to another Collection
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Collection<String> c2 = new ArrayList<>();
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c2.addAll(Countries.names(6));
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c.addAll(c2);
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print(c);
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c.remove(Countries.DATA[0][0]);
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print(c);
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c.remove(Countries.DATA[1][0]);
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print(c);
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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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print(c);
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c.addAll(c2);
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print(c);
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// Is an element in this Collection?
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String val = Countries.DATA[3][0];
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print("c.contains(" + val + ") = " + c.contains(val));
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// Is a Collection in this Collection?
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print("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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print(c2);
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// Throw away all the elements
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// in c2 that also appear in c3:
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c2.removeAll(c3);
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print("c2.isEmpty() = " + c2.isEmpty());
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c = new ArrayList<>();
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c.addAll(Countries.names(6));
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print(c);
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c.clear(); // Remove all elements
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print("after c.clear():" + c);
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}
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} /* Output:
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[ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI, ten, eleven]
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Collections.max(c) = ten
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Collections.min(c) = ALGERIA
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[ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI, ten, eleven, ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI]
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[ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI, ten, eleven, ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI]
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[BENIN, BOTSWANA, BURKINA FASO, BURUNDI, ten, eleven, ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI]
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[ten, eleven]
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[ten, eleven, ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI]
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c.contains(BOTSWANA) = true
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c.containsAll(c2) = true
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[ANGOLA, BENIN]
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c2.isEmpty() = true
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[ALGERIA, ANGOLA, BENIN, BOTSWANA, BURKINA FASO, BURUNDI]
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after c.clear():[]
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*///:~
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