// onjava/TypeCounter.java

// (c)2016 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://mindviewinc.com/Books/OnJava/ for more book information.

// Counts instances of a type family

package onjava;

import java.util.*;

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() {

StringBuilder result = new StringBuilder("{");

for(Map.Entry<Class<?>, Integer> pair : entrySet()) {

result.append(pair.getKey().getSimpleName());

result.append("=");

result.append(pair.getValue());

result.append(", ");

}

result.delete(result.length() - 2, result.length());

result.append("}");

return result.toString();

}

}