Find a value of the given type in the given Collection. - Java java.util

Java examples for java.util:Collection Element

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Description

Find a value of the given type in the given Collection.

Demo Code


import java.util.Arrays;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;

public class Main{
    public static void main(String[] argv){
        Collection collection = java.util.Arrays.asList("asdf","book2s.com");
        Class type = String.class;
        System.out.println(findValueOfType(collection,type));
    }//from   w  w  w . jav  a2  s .  com
    /**
     * Find a value of the given type in the given Collection.
     * @param collection the Collection to search
     * @param type the type to look for
     * @return a value of the given type found, or <code>null</code> if none
     * @throws IllegalArgumentException if more than one value of the given type found
     */
    public static Object findValueOfType(Collection collection, Class type)
            throws IllegalArgumentException {
        if (isEmpty(collection)) {
            return null;
        }
        Class typeToUse = (type != null ? type : Object.class);
        Object value = null;
        for (Iterator it = collection.iterator(); it.hasNext();) {
            Object obj = it.next();
            if (typeToUse.isInstance(obj)) {
                if (value != null) {
                    throw new IllegalArgumentException(
                            "More than one value of type ["
                                    + typeToUse.getName() + "] found");
                }
                value = obj;
            }
        }
        return value;
    }
    /**
     * Find a value of one of the given types in the given Collection:
     * searching the Collection for a value of the first type, then
     * searching for a value of the second type, etc.
     * @param collection the collection to search
     * @param types the types to look for, in prioritized order
     * @return a of one of the given types found, or <code>null</code> if none
     * @throws IllegalArgumentException if more than one value of the given type found
     */
    public static Object findValueOfType(Collection collection,
            Class[] types) throws IllegalArgumentException {
        if (isEmpty(collection) || ObjectUtils.isEmpty(types)) {
            return null;
        }
        for (int i = 0; i < types.length; i++) {
            Object value = findValueOfType(collection, types[i]);
            if (value != null) {
                return value;
            }
        }
        return null;
    }
    /**
     * Return <code>true</code> if the supplied Collection is <code>null</code>
     * or empty. Otherwise, return <code>false</code>.
     * @param collection the Collection to check
     * @return whether the given Collection is empty
     */
    public static boolean isEmpty(Collection collection) {
        return (collection == null || collection.isEmpty());
    }
    /**
     * Return <code>true</code> if the supplied Map is <code>null</code>
     * or empty. Otherwise, return <code>false</code>.
     * @param map the Map to check
     * @return whether the given Map is empty
     */
    public static boolean isEmpty(Map map) {
        return (map == null || map.isEmpty());
    }
}

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