Here you can find the source of join(final String separator, final Collection
| Parameter | Description |
|---|---|
| separator | the string to use to separate objects |
| objects | a collection of objects. the element order is defined by the iterator over objects |
| T | the type of the objects |
public static <T> String join(final String separator, final Collection<T> objects)
//package com.java2s; /*/*from w w w . j av a2 s .c om*/ * Copyright (c) 2017 NCIC, Institute of Computing Technology, Chinese Academy of Sciences * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ import java.util.AbstractList; import java.util.Arrays; import java.util.Collection; import java.util.Iterator; import java.util.LinkedList; import java.util.List; public class Main { /** * join an array of strings given a seperator * @param separator the string to insert between each array element * @param strings the array of strings * @return a string, which is the joining of all array values with the separator */ public static String join(String separator, String[] strings) { return join(separator, strings, 0, strings.length); } public static String join(String separator, String[] strings, int start, int end) { if ((end - start) == 0) { return ""; } StringBuilder ret = new StringBuilder(strings[start]); for (int i = start + 1; i < end; ++i) { ret.append(separator); ret.append(strings[i]); } return ret.toString(); } public static String join(String separator, int[] ints) { if (ints == null || ints.length == 0) return ""; else { StringBuilder ret = new StringBuilder(); ret.append(ints[0]); for (int i = 1; i < ints.length; ++i) { ret.append(separator); ret.append(ints[i]); } return ret.toString(); } } /** * Returns a string of the values in joined by separator, such as A,B,C * * @param separator separator character * @param doubles the array with values * @return a string with the values separated by the separator */ public static String join(String separator, double[] doubles) { if (doubles == null || doubles.length == 0) return ""; else { StringBuilder ret = new StringBuilder(); ret.append(doubles[0]); for (int i = 1; i < doubles.length; ++i) { ret.append(separator); ret.append(doubles[i]); } return ret.toString(); } } /** * Returns a string of the form elt1.toString() [sep elt2.toString() ... sep elt.toString()] for a collection of * elti objects (note there's no actual space between sep and the elti elements). Returns * "" if collection is empty. If collection contains just elt, then returns elt.toString() * * @param separator the string to use to separate objects * @param objects a collection of objects. the element order is defined by the iterator over objects * @param <T> the type of the objects * @return a non-null string */ public static <T> String join(final String separator, final Collection<T> objects) { if (objects.isEmpty()) { // fast path for empty collection return ""; } else { final Iterator<T> iter = objects.iterator(); final T first = iter.next(); if (!iter.hasNext()) // fast path for singleton collections return first.toString(); else { // full path for 2+ collection that actually need a join final StringBuilder ret = new StringBuilder(first.toString()); while (iter.hasNext()) { ret.append(separator); ret.append(iter.next().toString()); } return ret.toString(); } } } public static <T> String join(final String separator, final T... objects) { return join(separator, Arrays.asList(objects)); } /** * Create a new list that contains the elements of left along with elements elts * @param left a non-null list of elements * @param elts a varargs vector for elts to append in order to left * @return A newly allocated linked list containing left followed by elts */ public static <T> List<T> append(final List<T> left, T... elts) { final List<T> l = new LinkedList<T>(left); l.addAll(Arrays.asList(elts)); return l; } /** * Returns a {@link List List<Integer>} representation of an primitive int array. * @param values the primitive int array to represent. * @return never code {@code null}. The returned list will be unmodifiable yet it will reflect changes in values in the original array yet * you cannot change the values */ public static List<Integer> asList(final int... values) { if (values == null) throw new IllegalArgumentException("the input array cannot be null"); return new AbstractList<Integer>() { @Override public Integer get(final int index) { return values[index]; } @Override public int size() { return values.length; } }; } /** * Returns a {@link List List<Double>} representation of an primitive double array. * @param values the primitive int array to represent. * @return never code {@code null}. The returned list will be unmodifiable yet it will reflect changes in values in the original array yet * you cannot change the values. */ public static List<Double> asList(final double... values) { if (values == null) throw new IllegalArgumentException("the input array cannot be null"); return new AbstractList<Double>() { @Override public Double get(final int index) { return values[index]; } @Override public int size() { return values.length; } }; } /** * Adds element from an array into a collection. * * In the event of exception being throw due to some element, <code>dest</code> might have been modified by * the successful addition of element before that one. * * @param dest the destination collection which cannot be <code>null</code> and should be able to accept * the input elements. * @param elements the element to add to <code>dest</code> * @param <T> collection type element. * @throws UnsupportedOperationException if the <tt>add</tt> operation * is not supported by <code>dest</code>. * @throws ClassCastException if the class of any of the elements * prevents it from being added to <code>dest</code>. * @throws NullPointerException if any of the elements is <code>null</code> and <code>dest</code> * does not permit <code>null</code> elements * @throws IllegalArgumentException if some property of any of the elements * prevents it from being added to this collection * @throws IllegalStateException if any of the elements cannot be added at this * time due to insertion restrictions. * @return <code>true</code> if the collection was modified as a result. */ public static <T> boolean addAll(Collection<T> dest, T... elements) { boolean result = false; for (final T e : elements) { result = dest.add(e) | result; } return result; } }