Java tutorial
//package com.java2s; import java.util.Collection; import java.util.Iterator; public class Main { /** * <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 ""; } 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); } /** * <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 = ""; } // 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 ""; } 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(); } /** * <p> * Joins the elements of the provided <code>Iterator</code> into a single * String containing the provided elements. * </p> * <p> * No delimiter is added before or after the list. Null objects or empty * strings within the iteration are represented by empty strings. * </p> * <p> * See the examples here: {@link #join(Object[],char)}. * </p> * * @param iterator the <code>Iterator</code> of values to join together, may * be null * @param separator the separator character to use * @return the joined String, <code>null</code> if null iterator input * @since 2.0 */ public static String join(Iterator<?> iterator, char separator) { // handle null, zero and one elements before building a buffer if (iterator == null) { return null; } if (!iterator.hasNext()) { return ""; } Object first = iterator.next(); if (!iterator.hasNext()) { return first.toString(); } // two or more elements StringBuffer buf = new StringBuffer(256); // Java default is 16, // probably too small if (first != null) { buf.append(first); } while (iterator.hasNext()) { buf.append(separator); Object obj = iterator.next(); if (obj != null) { buf.append(obj); } } return buf.toString(); } /** * <p> * Joins the elements of the provided <code>Iterator</code> into a single * String containing the provided elements. * </p> * <p> * No delimiter is added before or after the list. A <code>null</code> * separator is the same as an empty String (""). * </p> * <p> * See the examples here: {@link #join(Object[],String)}. * </p> * * @param iterator the <code>Iterator</code> 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 iterator input */ public static String join(Iterator<?> iterator, String separator) { // handle null, zero and one elements before building a buffer if (iterator == null) { return null; } if (!iterator.hasNext()) { return ""; } Object first = iterator.next(); if (!iterator.hasNext()) { return first.toString(); } // two or more elements StringBuffer buf = new StringBuffer(256); // Java default is 16, // probably too small if (first != null) { buf.append(first); } while (iterator.hasNext()) { if (separator != null) { buf.append(separator); } Object obj = iterator.next(); if (obj != null) { buf.append(obj); } } return buf.toString(); } /** * <p> * Joins the elements of the provided <code>Collection</code> into a single * String containing the provided elements. * </p> * <p> * No delimiter is added before or after the list. Null objects or empty * strings within the iteration are represented by empty strings. * </p> * <p> * See the examples here: {@link #join(Object[],char)}. * </p> * * @param collection the <code>Collection</code> of values to join together, * may be null * @param separator the separator character to use * @return the joined String, <code>null</code> if null iterator input * @since 2.3 */ public static String join(Collection<?> collection, char separator) { if (collection == null) { return null; } return join(collection.iterator(), separator); } /** * <p> * Joins the elements of the provided <code>Collection</code> into a single * String containing the provided elements. * </p> * <p> * No delimiter is added before or after the list. A <code>null</code> * separator is the same as an empty String (""). * </p> * <p> * See the examples here: {@link #join(Object[],String)}. * </p> * * @param collection the <code>Collection</code> 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 iterator input * @since 2.3 */ public static String join(Collection<?> collection, String separator) { if (collection == null) { return null; } return join(collection.iterator(), separator); } }