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package test;

import java.util.HashSet;
import java.util.Set;

/**
 *
 * @author huanghuankun
 */
public class HashSetTest {

    public static void main(String[] args) {
        HashSet<Number> set = new HashSet<Number>();
        byte num_byte = 1;
        int num_int = 1;
        Integer num_int1 = 1;
        long num_long = 1;
        set.add(num_byte);
        set.add(num_int);
        set.add(num_int1);//包装类和其对应的基本类型，在set中视为重复，不同类型hashcode不同
        set.add(num_long);
        System.out.println("set.sieze()=" + set.size());
    }
}

输出：

set.sieze()=3