Java 相关计数问题及其实现

0. 一个类作为一个计数器

class Counter {
private static long counter;
private final long id = counter ++;

@Override
public String toString() {
return getClass().getSimpleName()+" " + id;
}

}

1. 使用 map

public class StringCounter extends HashMap<String, Integer>{

public void count(String name) {
Integer quantity = get(name);
if (quantity == null) {
put(name, 1);
} else {
put (name, quantity + 1);
}
}
}