取出list中的null

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package com.boventech.learning.util;import java.io.Serializable;import java.util.AbstractList;import java.util.RandomAccess;public class NullCollection extends AbstractList<Object> implements RandomAccess, Serializable{/** *  */private static final long serialVersionUID = 1L;@Overridepublic Object get(int index) {// TODO Auto-generated method stubreturn null;}@Overridepublic int size() {// TODO Auto-generated method stubreturn 1;}public boolean contains(Object obj) {          return null == obj;      }  private Object readResolve() {          return null;      } }

package com.boventech.learning.util;import java.util.Collection;  import java.util.List;    public class YHDCollectionUtils {             @SuppressWarnings("rawtypes")public static final Collection NULL_COLLECTION = new NullCollection();                @SuppressWarnings("unchecked")public static final <T> Collection<T> nullCollection() {          return (List<T>) NULL_COLLECTION;      }  }

package com.boventech.learning.test;import java.util.ArrayList;import java.util.List;import com.boventech.learning.util.YHDCollectionUtils;public class NullTest {/** * @param args */public static void main(String[] args) {      List<Integer> arrays = new ArrayList<Integer>();      arrays.add(2);      arrays.add(null);      arrays.add(456);      arrays.add(null);      arrays.add(789);      arrays.removeAll(YHDCollectionUtils.nullCollection());      System.out.println(arrays);  } }

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