Java tutorial
/* Copyright 2016 Sven van der Meer <vdmeer.sven@mykolab.com> * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package de.vandermeer.skb.interfaces.transformers.textformat; import org.apache.commons.lang3.StringUtils; import org.apache.commons.lang3.Validate; import org.apache.commons.lang3.text.StrBuilder; import de.vandermeer.skb.interfaces.transformers.IsTransformer; /** * Converts a string to a justified string of given length. * If the given string length is less than the required length, it will be stretched by inserting white spaces. * The returned string will be of the required length, blank strings will have only blanks characters. * * The method can be further customized by * - Setting an inner white space character - replace all white spaces in the text with that character * * The default length is {@link #DEFAULT_LENGTH}. * The default inner white space character is {@link #DEFAULT_INNER_WHITESPACE_CHARACTER}. * * The actual return object is of type {@link StrBuilder} to minimize the creation of lots of strings for more complex transformations. * An implementation can chose to provide a builder to append the padded string to as well. * * @author Sven van der Meer <vdmeer.sven@mykolab.com> * @version v0.0.2 build 170502 (02-May-17) for Java 1.8 * @since v0.0.1 */ public interface String_To_Justified extends IsTransformer<String, StrBuilder> { /** The default width, set to 80. */ static int DEFAULT_LENGTH = 80; /** Default white space replacement character, set to ' '. */ static char DEFAULT_INNER_WHITESPACE_CHARACTER = ' '; /** * Returns the required length for the conversion. * @return length, default is {@link #DEFAULT_LENGTH} */ default int getLength() { return DEFAULT_LENGTH; } /** * Returns the white space replacement character. * @return white space replacement character, default is {@link #DEFAULT_INNER_WHITESPACE_CHARACTER} */ default Character getInnerWsChar() { return DEFAULT_INNER_WHITESPACE_CHARACTER; } /** * Returns a builder to append the justified string to, rather than creating a new builder. * @return builder, can be null, if not null the justified string will be appended to it */ default StrBuilder getBuilderForAppend() { return null; } @Override default StrBuilder transform(String s) { IsTransformer.super.transform(s); StrBuilder ret = (this.getBuilderForAppend() == null) ? new StrBuilder(this.getLength()) : this.getBuilderForAppend(); // set string and replace all inner ws with required character String[] ar = StringUtils.split((s == null) ? "" : s); int length = 0; for (String str : ar) { length += str.length(); } //first spaces to distributed (even) //do that until all firsts have been consumed int l = ((ar.length - 1) == 0) ? 1 : (ar.length - 1); // null safe dividend int first = ((this.getLength() - length) / l) * (ar.length - 1); while (first > 0) { for (int i = 0; i < ar.length - 1; i++) { if (first != 0) { ar[i] += this.getInnerWsChar(); first--; } } } //second space to distributed (leftovers, as many as there are) //do seconds from the back to front, until all seconds have been consumed //reverse means do not append to the last array element! int second = (this.getLength() - length) % l; while (second > 0) { for (int i = ar.length - 2; i > 0; i--) { if (second != 0) { ar[i] += this.getInnerWsChar(); second--; } } } ret.append(StringUtils.join(ar)); while (ret.length() < this.getLength()) { ret.append(' '); } return ret; } /** * Creates a transformer that converts a string to a justified string of given length. * @param length the required length (must be >0) * @param innerWsChar inner white space replacement character * @param builder an optional builder to append the padded string to, used if set, ignored if null * @return new transformer * @see String_To_Justified interface description for how the converter works * @throws NullPointerException if an argument was unexpectedly null * @throws IllegalArgumentException if an argument was illegal */ static String_To_Justified create(int length, Character innerWsChar, StrBuilder builder) { Validate.validState(length > 0, "cannot work with lenght of less than 1"); return new String_To_Justified() { @Override public int getLength() { return (length < 1) ? String_To_Justified.super.getLength() : length; } @Override public StrBuilder getBuilderForAppend() { return builder; } @Override public Character getInnerWsChar() { return (innerWsChar == null) ? String_To_Justified.super.getInnerWsChar() : innerWsChar; } }; } /** * Returns justified string of given length. * @param s input string * @param length the required length (must be >0) * @return justified string * @see String_To_Justified interface description for how the conversion works * @throws NullPointerException if an argument was unexpectedly null * @throws IllegalArgumentException if an argument was illegal */ static StrBuilder convert(String s, int length) { return String_To_Justified.create(length, null, null).transform(s); } /** * Returns justified string of given length. * @param s input string * @param length the required length (must be >0) * @param innerWsChar inner white space replacement character, default is used if null * @return justified string * @see String_To_Justified interface description for how the conversion works * @throws NullPointerException if an argument was unexpectedly null * @throws IllegalArgumentException if an argument was illegal */ static StrBuilder convert(String s, int length, Character innerWsChar) { return String_To_Justified.create(length, innerWsChar, null).transform(s); } /** * Returns justified string of given length. * @param s input string * @param length the required length (must be >0) * @param builder an optional builder to append the padded string to, used if set, ignored if null * @return justified string * @see String_To_Justified interface description for how the conversion works * @throws NullPointerException if an argument was unexpectedly null * @throws IllegalArgumentException if an argument was illegal */ static StrBuilder convert(String s, int length, StrBuilder builder) { return String_To_Justified.create(length, null, builder).transform(s); } /** * Returns justified string of given length. * @param s input string * @param length the required length (must be >0) * @param innerWsChar inner white space replacement character, default is used if null * @param builder an optional builder to append the padded string to, used if set, ignored if null * @return justified string * @see String_To_Justified interface description for how the conversion works * @throws NullPointerException if an argument was unexpectedly null * @throws IllegalArgumentException if an argument was illegal */ static StrBuilder convert(String s, int length, Character innerWsChar, StrBuilder builder) { return String_To_Justified.create(length, innerWsChar, builder).transform(s); } }