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 centered string of given length. * If the given string length is less than the required length, padding characters will be added to the right and to the left. * By default, the returned string will be of the required length, blank strings will have only left padding 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 right padding character is {@link #DEFAULT_RIGHT_PADDING_CHARACTER}. * The default left padding character is {@link #DEFAULT_LEFT_PADDING_CHARACTER}. * 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_Centered extends IsTransformer<String, StrBuilder> { /** The default width, set to 80. */ static int DEFAULT_LENGTH = 80; /** Default right padding character, set to ' '. */ static char DEFAULT_RIGHT_PADDING_CHARACTER = ' '; /** Default left padding character, set to ' '. */ static char DEFAULT_LEFT_PADDING_CHARACTER = ' '; /** 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 the right padding character for the conversion. * @return right padding character, cannot be null, default is {@link #DEFAULT_RIGHT_PADDING_CHARACTER} */ default Character getRightPaddingChar() { return DEFAULT_RIGHT_PADDING_CHARACTER; } /** * Returns the left padding character for the conversion. * @return left padding character, cannot be null, default is {@link #DEFAULT_LEFT_PADDING_CHARACTER} */ default Character getLeftPaddingChar() { return DEFAULT_LEFT_PADDING_CHARACTER; } /** * Returns a builder to append the centered string to, rather than creating a new builder. * @return builder, can be null, if not null the centered 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 center = (s == null) ? "" : s; center = center.replace(' ', this.getInnerWsChar()); //get a char[] with a centered string, using paddingLedft in left and right side char[] car = StringUtils.center(center, this.getLength()).toCharArray(); //change all right padding chars to the actual right padding char for (int i = car.length - 1; i > 0; i--) { if (car[i] == ' ') { car[i] = this.getRightPaddingChar(); } else { break; } } //change all remaining tmp padding chars to the actual left padding char for (int i = 0; i < car.length; i++) { if (car[i] == ' ') { car[i] = this.getLeftPaddingChar(); } else { break; } } //add this new string to the render object ret.append(car); return ret; } /** * Creates a transformer that converts a string to a centered string of given length. * @param length the required length (must be >0) * @param leftPaddingChar the left padding character, default is used if null * @param rightPaddingChar the right padding character, default is used if null * @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_Centered 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_Centered create(int length, Character leftPaddingChar, Character rightPaddingChar, Character innerWsChar, StrBuilder builder) { Validate.validState(length > 0, "cannot work with lenght of less than 1"); return new String_To_Centered() { @Override public Character getInnerWsChar() { return (innerWsChar == null) ? String_To_Centered.super.getInnerWsChar() : innerWsChar; } @Override public int getLength() { return (length < 1) ? String_To_Centered.super.getLength() : length; } @Override public Character getLeftPaddingChar() { return (leftPaddingChar == null) ? String_To_Centered.super.getLeftPaddingChar() : leftPaddingChar; } @Override public Character getRightPaddingChar() { return (rightPaddingChar == null) ? String_To_Centered.super.getRightPaddingChar() : rightPaddingChar; } @Override public StrBuilder getBuilderForAppend() { return builder; } }; } /** * Returns centered string of given length using default padding characters. * @param s input string * @param length the required length (must be >0) * @return centered string * @see String_To_Centered 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_Centered.create(length, null, null, null, null).transform(s); } /** * Returns centered string of given length using default padding characters. * @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 centered string * @see String_To_Centered 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_Centered.create(length, null, null, null, builder).transform(s); } /** * Returns centered string of given length using the same padding character on both sides. * @param s input string * @param length the required length (must be >0) * @param paddingChar the padding character for left and right padding, default is used if null * @return centered string * @see String_To_Centered 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 paddingChar) { return String_To_Centered.create(length, paddingChar, paddingChar, null, null).transform(s); } /** * Returns centered string of given length using the same padding character on both sides. * @param s input string * @param length the required length (must be >0) * @param paddingChar the padding character for left and right padding, default is used if null * @param builder an optional builder to append the padded string to, used if set, ignored if null * @return centered string * @see String_To_Centered 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 paddingChar, StrBuilder builder) { return String_To_Centered.create(length, paddingChar, paddingChar, null, builder).transform(s); } /** * Returns centered string of given length with specific padding characters. * @param s input string * @param length the required length (must be >0) * @param leftPaddingChar the left padding character, default is used if null * @param rightPaddingChar the right padding character, default is used if null * @return centered string * @see String_To_Centered 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 leftPaddingChar, Character rightPaddingChar) { return String_To_Centered.create(length, leftPaddingChar, rightPaddingChar, null, null).transform(s); } /** * Returns centered string of given length with specific padding characters. * @param s input string * @param length the required length (must be >0) * @param leftPaddingChar the left padding character, default is used if null * @param rightPaddingChar the right padding character, default is used if null * @param innerWsChar inner white space replacement character, default is used if null * @return centered string * @see String_To_Centered 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 leftPaddingChar, Character rightPaddingChar, Character innerWsChar) { return String_To_Centered.create(length, leftPaddingChar, rightPaddingChar, innerWsChar, null).transform(s); } /** * Returns centered string of given length with specific padding characters. * @param s input string * @param length the required length (must be >0) * @param leftPaddingChar the left padding character, default is used if null * @param rightPaddingChar the right padding character, default is used if null * @param builder an optional builder to append the padded string to, used if set, ignored if null * @return centered string * @see String_To_Centered 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 leftPaddingChar, Character rightPaddingChar, StrBuilder builder) { return String_To_Centered.create(length, leftPaddingChar, rightPaddingChar, null, builder).transform(s); } /** * Returns centered string of given length with specific padding characters. * @param s input string * @param length the required length (must be >0) * @param leftPaddingChar the left padding character, default is used if null * @param rightPaddingChar the right padding character, default is used if null * @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 centered string * @see String_To_Centered 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 leftPaddingChar, Character rightPaddingChar, Character innerWsChar, StrBuilder builder) { return String_To_Centered.create(length, leftPaddingChar, rightPaddingChar, innerWsChar, builder) .transform(s); } }