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Copy pathTypesForSets.java
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executable file
·74 lines (70 loc) · 2.43 KB
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package containers;//: containers/TypesForSets.java
// Methods necessary to put your own type in a Set.
import java.util.*;
class SetType {
int i;
public SetType(int n) { i = n; }
public boolean equals(Object o) {
return o instanceof SetType && (i == ((SetType)o).i);
}
public String toString() { return Integer.toString(i); }
}
class HashType extends SetType {
public HashType(int n) { super(n); }
public int hashCode() { return i; }
}
class TreeType extends SetType
implements Comparable<TreeType> {
public TreeType(int n) { super(n); }
public int compareTo(TreeType arg) {
return (arg.i < i ? -1 : (arg.i == i ? 0 : 1));
}
}
public class TypesForSets {
static <T> Set<T> fill(Set<T> set, Class<T> type) {
try {
for(int i = 0; i < 10; i++)
set.add(
type.getConstructor(int.class).newInstance(i));
} catch(Exception e) {
throw new RuntimeException(e);
}
return set;
}
static <T> void test(Set<T> set, Class<T> type) {
fill(set, type);
fill(set, type); // Try to add duplicates
fill(set, type);
System.out.println(set);
}
public static void main(String[] args) {
test(new HashSet<HashType>(), HashType.class);
test(new LinkedHashSet<HashType>(), HashType.class);
test(new TreeSet<TreeType>(), TreeType.class);
// Things that don't work:
test(new HashSet<SetType>(), SetType.class);
test(new HashSet<TreeType>(), TreeType.class);
test(new LinkedHashSet<SetType>(), SetType.class);
test(new LinkedHashSet<TreeType>(), TreeType.class);
try {
test(new TreeSet<SetType>(), SetType.class);
} catch(Exception e) {
System.out.println(e.getMessage());
}
try {
test(new TreeSet<HashType>(), HashType.class);
} catch(Exception e) {
System.out.println(e.getMessage());
}
}
} /* Output: (Sample)
[2, 4, 9, 8, 6, 1, 3, 7, 5, 0]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
[9, 9, 7, 5, 1, 2, 6, 3, 0, 7, 2, 4, 4, 7, 9, 1, 3, 6, 2, 4, 3, 0, 5, 0, 8, 8, 8, 6, 5, 1]
[0, 5, 5, 6, 5, 0, 3, 1, 9, 8, 4, 2, 3, 9, 7, 3, 4, 4, 0, 7, 1, 9, 6, 2, 1, 8, 2, 8, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
java.lang.ClassCastException: SetType cannot be cast to java.lang.Comparable
java.lang.ClassCastException: HashType cannot be cast to java.lang.Comparable
*///:~