Java Collection Search getSingleElement(Collection collection)

Description

Returns the single element contained by the input collection

License

Open Source License

Parameter

Parameter	Description
T	a parameter
collection	a parameter

Exception

Parameter	Description
IndexOutOfBoundsException	if the collections contains either zerso or >1 elements

Declaration

public static <T> T getSingleElement(Collection<T> collection) 

Method Source Code

//package com.java2s;
import java.util.ArrayList;

import java.util.Collection;
import java.util.Collections;

import java.util.Iterator;

import java.util.List;

public class Main {
    /**//from   www  .  j  a va  2s .c om
     * Returns the single element contained by the input collection
     * 
     * @throws IndexOutOfBoundsException
     *             if the collections contains either zerso or >1 elements
     * @param <T>
     * @param collection
     * @return
     */
    public static <T> T getSingleElement(Collection<T> collection) {
        if (collection.size() != 1)
            throw new IndexOutOfBoundsException(
                    String.format("Expected collection to contain a single element, but observed %d elements: %s",
                            collection.size(), collection.toString()));
        return collection.iterator().next();
    }

    /**
     * Returns the single element contained by the input Iterable<T>
     * 
     * @throws IndexOutOfBoundsException
     *             if the iterable contains either zerso or >1 elements
     * @param <T>
     * @param collection
     * @return
     */
    public static <T> T getSingleElement(Iterable<T> iterable) {
        List<T> list = createList(iterable.iterator());
        return getSingleElement(list);
    }

    /**
     * Returns a String representation of the input collection by calling each
     * element's toString() method.
     * 
     * @param <T>
     * @param collection
     * @return
     */
    public static <T> Collection<String> toString(Collection<T> collection) {
        Collection<String> strings = new ArrayList<String>();
        for (T item : collection)
            strings.add(item.toString());
        return strings;
    }

    /**
     * Returns a List implementation for any input collection
     * 
     * @param <T>
     * @param collection
     * @return
     */
    public static <T> List<T> createList(Collection<T> collection) {
        return Collections.list(Collections.enumeration(collection));
    }

    /**
     * Returns an empty list
     * 
     * @param <T>
     * @return
     */
    public static <T> List<T> createList() {
        return Collections.emptyList();
    }

    /**
     * Returns a List<T> containing the input arguments.
     * 
     * @param <T>
     * @param item1
     * @return
     */
    public static <T> List<T> createList(T item1) {
        List<T> list = new ArrayList<T>();
        list.add(item1);
        return list;
    }

    /**
     * Returns a List<T> containing the input arguments.
     * 
     * @param <T>
     * @param item1
     * @param item2
     * @return
     */
    public static <T> List<T> createList(T item1, T item2) {
        List<T> list = new ArrayList<T>();
        list.add(item1);
        list.add(item2);
        return list;
    }

    /**
     * Returns a List<T> containing the input arguments.
     * 
     * @param <T>
     * @param item1
     * @param item2
     * @param item3
     * @return
     */
    public static <T> List<T> createList(T item1, T item2, T item3) {
        List<T> list = new ArrayList<T>();
        list.add(item1);
        list.add(item2);
        list.add(item3);
        return list;
    }

    /**
     * Returns a List<T> containing the input arguments.
     * 
     * @param <T>
     * @param item1
     * @param item2
     * @param item3
     * @param item4
     * @return
     */
    public static <T> List<T> createList(T item1, T item2, T item3, T item4) {
        List<T> list = new ArrayList<T>();
        list.add(item1);
        list.add(item2);
        list.add(item3);
        list.add(item4);
        return list;
    }

    /**
     * Returns a List<T> containing the input arguments.
     * 
     * @param <T>
     * @param item1
     * @param item2
     * @param item3
     * @param item4
     * @param item5
     * @return
     */
    public static <T> List<T> createList(T item1, T item2, T item3, T item4, T item5) {
        List<T> list = new ArrayList<T>();
        list.add(item1);
        list.add(item2);
        list.add(item3);
        list.add(item4);
        list.add(item5);
        return list;
    }

    /**
     * Returns a List<T> containing the input arguments.
     * 
     * @param <T>
     * @param item1
     * @param item2
     * @param item3
     * @param item4
     * @param item5
     * @param item6
     * @return
     */
    public static <T> List<T> createList(T item1, T item2, T item3, T item4, T item5, T item6) {
        List<T> list = new ArrayList<T>();
        list.add(item1);
        list.add(item2);
        list.add(item3);
        list.add(item4);
        list.add(item5);
        list.add(item6);
        return list;
    }

    /**
     * Returns a List<T> containing the input arguments.
     * 
     * @param <T>
     * @param item1
     * @param item2
     * @param item3
     * @param item4
     * @param item5
     * @param item6
     * @param item7
     * @return
     */
    public static <T> List<T> createList(T item1, T item2, T item3, T item4, T item5, T item6, T item7) {
        List<T> list = new ArrayList<T>();
        list.add(item1);
        list.add(item2);
        list.add(item3);
        list.add(item4);
        list.add(item5);
        list.add(item6);
        list.add(item7);
        return list;
    }

    /**
     * Returns a List<T> containing the input arguments.
     * 
     * @param <T>
     * @param item1
     * @param item2
     * @param item3
     * @param item4
     * @param item5
     * @param item6
     * @param item7
     * @param item8
     * @return
     */
    public static <T> List<T> createList(T item1, T item2, T item3, T item4, T item5, T item6, T item7, T item8) {
        List<T> list = new ArrayList<T>();
        list.add(item1);
        list.add(item2);
        list.add(item3);
        list.add(item4);
        list.add(item5);
        list.add(item6);
        list.add(item7);
        list.add(item8);
        return list;
    }

    /**
     * Returns a List<T> containing the input arguments.
     * 
     * @param <T>
     * @param item1
     * @param item2
     * @param item3
     * @param item4
     * @param item5
     * @param item6
     * @param item7
     * @param item8
     * @param item9
     * @return
     */
    public static <T> List<T> createList(T item1, T item2, T item3, T item4, T item5, T item6, T item7, T item8,
            T item9) {
        List<T> list = new ArrayList<T>();
        list.add(item1);
        list.add(item2);
        list.add(item3);
        list.add(item4);
        list.add(item5);
        list.add(item6);
        list.add(item7);
        list.add(item8);
        list.add(item9);
        return list;
    }

    /**
     * Returns a List<T> containing the input arguments.
     * 
     * @param <T>
     * @param item1
     * @param item2
     * @param item3
     * @param item4
     * @param item5
     * @param item6
     * @param item7
     * @param item8
     * @param item9
     * @param item10
     * @param otherItems
     * @return
     */
    public static <T> List<T> createList(T item1, T item2, T item3, T item4, T item5, T item6, T item7, T item8,
            T item9, T item10, T... otherItems) {
        List<T> list = new ArrayList<T>();
        list.add(item1);
        list.add(item2);
        list.add(item3);
        list.add(item4);
        list.add(item5);
        list.add(item6);
        list.add(item7);
        list.add(item8);
        list.add(item9);
        list.add(item10);
        for (T item : otherItems)
            list.add(item);
        return list;
    }

    /**
     * Returns the contents of an iterator as a list
     * 
     * @param <T>
     * @param iter
     * @return
     */
    public static <T> List<T> createList(Iterator<T> iter) {
        List<T> list = new ArrayList<T>();
        while (iter.hasNext()) {
            list.add(iter.next());
        }
        return list;
    }
}

Related

1. getSingle(Collection configs)
2. getSingleElement(Collection collection)
3. getSingleItem(Collection values)
4. getSingleValue(Iterable collection)
5. hasElements(Collection c)