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import java.util.*;
public class HashMapTest {
public static void main (String [] args) {
HashMap<String,String> hm = new HashMap<String,String>();
hm.put("zhangsan","sh");
hm.put("wangwu","fd");
hm.put("zhaoliu","hre");
hm.put("asi","gre");
hm.put("shabi","gre");
Set<String> hs = hm.keySet();
System.out.println(hs.size());
}
}
import java.util.HashMap;
import java.util.Set;
public class HashMapTest {
public static void main (String [] args) {
HashMap<String,String> hm = new HashMap<String,String>();
hm.put("zhangsan","sh");
hm.put("wangwu","fd");
hm.put("zhaoliu","hre");
hm.put("asi","gre");
hm.put("shabi","gre");
Set<String> hs = hm.keySet();
System.out.println(hs.getClass().getName());//加一句
System.out.println(hs.size());
}
}
private final class KeySet extends AbstractSet<K> {
public Iterator<K> iterator() {
return newKeyIterator();
}
public int size() {
return size;
}
public boolean contains(Object o) {
return containsKey(o);
}
public boolean remove(Object o) {
return HashMap.this.removeEntryForKey(o) != null;
}
public void clear() {
HashMap.this.clear();
}
public Set<K> keySet() {
Set<K> ks = keySet;
return (ks != null ? ks : (keySet = new KeySet()));
}