90 lines
2.7 KiB
Java
90 lines
2.7 KiB
Java
//: containersindepth/TypesForSets.java
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// ©2015 MindView LLC: see Copyright.txt
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// Methods necessary to put your own type in a Set.
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import java.lang.reflect.InvocationTargetException;
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import java.util.*;
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class SetType {
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int i;
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public SetType(int n) { i = n; }
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@Override
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public boolean equals(Object o) {
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return o instanceof SetType && (i == ((SetType)o).i);
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}
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@Override
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public String toString() { return Integer.toString(i); }
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}
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class HashType extends SetType {
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public HashType(int n) { super(n); }
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@Override
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public int hashCode() { return i; }
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}
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class TreeType extends SetType
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implements Comparable<TreeType> {
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public TreeType(int n) { super(n); }
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@Override
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public int compareTo(TreeType arg) {
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return (arg.i < i ? -1 : (arg.i == i ? 0 : 1));
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}
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}
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public class TypesForSets {
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static <T> Set<T> fill(Set<T> set, Class<T> type) {
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try {
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for(int i = 0; i < 10; i++)
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set.add(
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type.getConstructor(int.class).newInstance(i));
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} catch(NoSuchMethodException |
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SecurityException |
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InstantiationException |
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IllegalAccessException |
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IllegalArgumentException |
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InvocationTargetException e) {
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throw new RuntimeException(e);
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}
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return set;
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}
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static <T> void test(Set<T> set, Class<T> type) {
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fill(set, type);
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fill(set, type); // Try to add duplicates
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fill(set, type);
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System.out.println(set);
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}
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public static void main(String[] args) {
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test(new HashSet<>(), HashType.class);
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test(new LinkedHashSet<>(), HashType.class);
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test(new TreeSet<>(), TreeType.class);
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// Things that don't work:
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test(new HashSet<>(), SetType.class);
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test(new HashSet<>(), TreeType.class);
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test(new LinkedHashSet<>(), SetType.class);
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test(new LinkedHashSet<>(), TreeType.class);
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try {
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test(new TreeSet<>(), SetType.class);
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} catch(Exception e) {
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System.out.println("Expected: " + e.getMessage());
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}
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try {
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test(new TreeSet<>(), HashType.class);
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} catch(Exception e) {
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System.out.println("Expected: " + e.getMessage());
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}
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}
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} /* Output:
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[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
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[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
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[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
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[9, 5, 3, 1, 8, 7, 1, 3, 5, 0, 2, 0, 7, 4, 6, 8, 3, 7, 5,
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4, 2, 9, 6, 0, 9, 1, 8, 6, 2, 4]
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[0, 2, 5, 1, 2, 4, 7, 4, 5, 6, 3, 1, 4, 1, 6, 3, 8, 9, 0,
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9, 6, 3, 5, 0, 8, 7, 9, 7, 8, 2]
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[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8,
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9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
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[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8,
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9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
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Expected: SetType cannot be cast to java.lang.Comparable
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Expected: HashType cannot be cast to java.lang.Comparable
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*///:~
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