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TypeCounter.java
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41 lines (40 loc) · 1.25 KB
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// onjava/TypeCounter.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Counts instances of a type family
package onjava;
import java.util.*;
import java.util.stream.*;
public class
TypeCounter extends HashMap<Class<?>, Integer> {
private Class<?> baseType;
public TypeCounter(Class<?> baseType) {
this.baseType = baseType;
}
public void count(Object obj) {
Class<?> type = obj.getClass();
if(!baseType.isAssignableFrom(type))
throw new RuntimeException(
obj + " incorrect type: " + type +
", should be type or subtype of " + baseType);
countClass(type);
}
private void countClass(Class<?> type) {
Integer quantity = get(type);
put(type, quantity == null ? 1 : quantity + 1);
Class<?> superClass = type.getSuperclass();
if(superClass != null &&
baseType.isAssignableFrom(superClass)) {
countClass(superClass);
}
}
@Override public String toString() {
String result = entrySet().stream()
.map(pair -> String.format("%s=%s",
pair.getKey().getSimpleName(),
pair.getValue()))
.collect(Collectors.joining(", "));
return "{" + result + "}";
}
}