Java Array Concatenate concatenate(Object[] array)

Description

Concatenates elements of an array into a single String.

License

Open Source License

Parameter

Parameter	Description
array	the array of values to concatenate, may be null

Return

the concatenated String, null if null array input

Declaration

@Deprecated
public static String concatenate(Object[] array) 

Method Source Code

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

public class Main {
    /**/*from w ww.ja  v a2s .c  om*/
     * The empty String <code>""</code>.
     * @since 2.0
     */
    public static final String EMPTY = "";

    /**
     * <p>Concatenates elements of an array into a single String.
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.concatenate(null)            = null
     * StringUtils.concatenate([])              = ""
     * StringUtils.concatenate([null])          = ""
     * StringUtils.concatenate(["a", "b", "c"]) = "abc"
     * StringUtils.concatenate([null, "", "a"]) = "a"
     * </pre>
     *
     * @param array  the array of values to concatenate, may be null
     * @return the concatenated String, <code>null</code> if null array input
     * @deprecated Use the better named {@link #join(Object[])} instead.
     *             Method will be removed in Commons Lang 3.0.
     */
    @Deprecated
    public static String concatenate(Object[] array) {
        return join(array, null);
    }

    /**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No separator is added to the joined String.
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null)            = null
     * StringUtils.join([])              = ""
     * StringUtils.join([null])          = ""
     * StringUtils.join(["a", "b", "c"]) = "abc"
     * StringUtils.join([null, "", "a"]) = "a"
     * </pre>
     *
     * @param array  the array of values to join together, may be null
     * @return the joined String, <code>null</code> if null array input
     * @since 2.0
     */
    public static String join(Object[] array) {
        return join(array, null);
    }

    /**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
     * StringUtils.join(["a", "b", "c"], null) = "abc"
     * StringUtils.join([null, "", "a"], ';')  = ";;a"
     * </pre>
     *
     * @param array  the array of values to join together, may be null
     * @param separator  the separator character to use
     * @return the joined String, <code>null</code> if null array input
     * @since 2.0
     */
    public static String join(Object[] array, char separator) {
        if (array == null) {
            return null;
        }

        return join(array, separator, 0, array.length);
    }

    /**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *)               = null
     * StringUtils.join([], *)                 = ""
     * StringUtils.join([null], *)             = ""
     * StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
     * StringUtils.join(["a", "b", "c"], null) = "abc"
     * StringUtils.join([null, "", "a"], ';')  = ";;a"
     * </pre>
     *
     * @param array  the array of values to join together, may be null
     * @param separator  the separator character to use
     * @param startIndex the first index to start joining from.  It is
     * an error to pass in an end index past the end of the array
     * @param endIndex the index to stop joining from (exclusive). It is
     * an error to pass in an end index past the end of the array
     * @return the joined String, <code>null</code> if null array input
     * @since 2.0
     */
    public static String join(Object[] array, char separator, int startIndex, int endIndex) {
        if (array == null) {
            return null;
        }
        int bufSize = (endIndex - startIndex);
        if (bufSize <= 0) {
            return EMPTY;
        }

        bufSize *= ((array[startIndex] == null ? 16 : array[startIndex].toString().length()) + 1);
        StringBuffer buf = new StringBuffer(bufSize);

        for (int i = startIndex; i < endIndex; i++) {
            if (i > startIndex) {
                buf.append(separator);
            }
            if (array[i] != null) {
                buf.append(array[i]);
            }
        }
        return buf.toString();
    }

    /**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * A <code>null</code> separator is the same as an empty String ("").
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *)                = null
     * StringUtils.join([], *)                  = ""
     * StringUtils.join([null], *)              = ""
     * StringUtils.join(["a", "b", "c"], "--")  = "a--b--c"
     * StringUtils.join(["a", "b", "c"], null)  = "abc"
     * StringUtils.join(["a", "b", "c"], "")    = "abc"
     * StringUtils.join([null, "", "a"], ',')   = ",,a"
     * </pre>
     *
     * @param array  the array of values to join together, may be null
     * @param separator  the separator character to use, null treated as ""
     * @return the joined String, <code>null</code> if null array input
     */
    public static String join(Object[] array, String separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    @SuppressWarnings("unchecked")
    public static String join(List list, String separator) {
        if (list == null) {
            return null;
        }
        return join(list.toArray(), separator, 0, list.size());
    }

    /**
     * <p>Joins the elements of the provided array into a single String
     * containing the provided list of elements.</p>
     *
     * <p>No delimiter is added before or after the list.
     * A <code>null</code> separator is the same as an empty String ("").
     * Null objects or empty strings within the array are represented by
     * empty strings.</p>
     *
     * <pre>
     * StringUtils.join(null, *)                = null
     * StringUtils.join([], *)                  = ""
     * StringUtils.join([null], *)              = ""
     * StringUtils.join(["a", "b", "c"], "--")  = "a--b--c"
     * StringUtils.join(["a", "b", "c"], null)  = "abc"
     * StringUtils.join(["a", "b", "c"], "")    = "abc"
     * StringUtils.join([null, "", "a"], ',')   = ",,a"
     * </pre>
     *
     * @param array  the array of values to join together, may be null
     * @param separator  the separator character to use, null treated as ""
     * @param startIndex the first index to start joining from.  It is
     * an error to pass in an end index past the end of the array
     * @param endIndex the index to stop joining from (exclusive). It is
     * an error to pass in an end index past the end of the array
     * @return the joined String, <code>null</code> if null array input
     */
    public static String join(Object[] array, String separator, int startIndex, int endIndex) {
        if (array == null) {
            return null;
        }
        if (separator == null) {
            separator = EMPTY;
        }

        // endIndex - startIndex > 0:   Len = NofStrings *(len(firstString) + len(separator))
        //           (Assuming that all Strings are roughly equally long)
        int bufSize = (endIndex - startIndex);
        if (bufSize <= 0) {
            return EMPTY;
        }

        bufSize *= ((array[startIndex] == null ? 16 : array[startIndex].toString().length()) + separator.length());

        StringBuffer buf = new StringBuffer(bufSize);

        for (int i = startIndex; i < endIndex; i++) {
            if (i > startIndex) {
                buf.append(separator);
            }
            if (array[i] != null) {
                buf.append(array[i]);
            }
        }
        return buf.toString();
    }
}

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6. concatenate(Object[] array)
7. concatenate(Object[] array)
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9. concatenate(Object[] collection)