1 /** 2 * 3 * Licensed to the Apache Software Foundation (ASF) under one 4 * or more contributor license agreements. See the NOTICE file 5 * distributed with this work for additional information 6 * regarding copyright ownership. The ASF licenses this file 7 * to you under the Apache License, Version 2.0 (the 8 * "License"); you may not use this file except in compliance 9 * with the License. You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, software 14 * distributed under the License is distributed on an "AS IS" BASIS, 15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 * See the License for the specific language governing permissions and 17 * limitations under the License. 18 */ 19 package org.apache.hadoop.hbase.util; 20 21 import org.apache.hadoop.hbase.classification.InterfaceAudience; 22 23 /** 24 * Utility for Strings. 25 */ 26 @InterfaceAudience.Private 27 public class Strings { 28 public final static String DEFAULT_SEPARATOR = "="; 29 public final static String DEFAULT_KEYVALUE_SEPARATOR = ", "; 30 31 /** 32 * Append to a StringBuilder a key/value. 33 * Uses default separators. 34 * @param sb StringBuilder to use 35 * @param key Key to append. 36 * @param value Value to append. 37 * @return Passed <code>sb</code> populated with key/value. 38 */ 39 public static StringBuilder appendKeyValue(final StringBuilder sb, 40 final String key, final Object value) { 41 return appendKeyValue(sb, key, value, DEFAULT_SEPARATOR, 42 DEFAULT_KEYVALUE_SEPARATOR); 43 } 44 45 /** 46 * Append to a StringBuilder a key/value. 47 * Uses default separators. 48 * @param sb StringBuilder to use 49 * @param key Key to append. 50 * @param value Value to append. 51 * @param separator Value to use between key and value. 52 * @param keyValueSeparator Value to use between key/value sets. 53 * @return Passed <code>sb</code> populated with key/value. 54 */ 55 public static StringBuilder appendKeyValue(final StringBuilder sb, 56 final String key, final Object value, final String separator, 57 final String keyValueSeparator) { 58 if (sb.length() > 0) { 59 sb.append(keyValueSeparator); 60 } 61 return sb.append(key).append(separator).append(value); 62 } 63 64 /** 65 * Given a PTR string generated via reverse DNS lookup, return everything 66 * except the trailing period. Example for host.example.com., return 67 * host.example.com 68 * @param dnPtr a domain name pointer (PTR) string. 69 * @return Sanitized hostname with last period stripped off. 70 * 71 */ 72 public static String domainNamePointerToHostName(String dnPtr) { 73 if (dnPtr == null) 74 return null; 75 return dnPtr.endsWith(".") ? dnPtr.substring(0, dnPtr.length()-1) : dnPtr; 76 } 77 78 /** 79 * Null-safe length check. 80 * @param input 81 * @return true if null or length==0 82 */ 83 public static boolean isEmpty(String input) { 84 return input == null || input.length() == 0; 85 } 86 87 /** 88 * Push the input string to the right by appending a character before it, usually a space. 89 * @param input the string to pad 90 * @param padding the character to repeat to the left of the input string 91 * @param length the desired total length including the padding 92 * @return padding characters + input 93 */ 94 public static String padFront(String input, char padding, int length) { 95 if (input.length() > length) { 96 throw new IllegalArgumentException("input \"" + input + "\" longer than maxLength=" + length); 97 } 98 int numPaddingCharacters = length - input.length(); 99 return repeat(padding, numPaddingCharacters) + input; 100 } 101 102 /** 103 * @param c repeat this character 104 * @param reapeatFor the length of the output String 105 * @return c, repeated repeatFor times 106 */ 107 public static String repeat(char c, int reapeatFor) { 108 StringBuilder sb = new StringBuilder(); 109 for (int i = 0; i < reapeatFor; ++i) { 110 sb.append(c); 111 } 112 return sb.toString(); 113 } 114 }