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.classification.InterfaceAudience;
22 import org.apache.hadoop.classification.InterfaceStability;
23
24 /**
25 * Utility for Strings.
26 */
27 @InterfaceAudience.Public
28 @InterfaceStability.Stable
29 public class Strings {
30 public final static String DEFAULT_SEPARATOR = "=";
31 public final static String DEFAULT_KEYVALUE_SEPARATOR = ", ";
32
33 /**
34 * Append to a StringBuilder a key/value.
35 * Uses default separators.
36 * @param sb StringBuilder to use
37 * @param key Key to append.
38 * @param value Value to append.
39 * @return Passed <code>sb</code> populated with key/value.
40 */
41 public static StringBuilder appendKeyValue(final StringBuilder sb,
42 final String key, final Object value) {
43 return appendKeyValue(sb, key, value, DEFAULT_SEPARATOR,
44 DEFAULT_KEYVALUE_SEPARATOR);
45 }
46
47 /**
48 * Append to a StringBuilder a key/value.
49 * Uses default separators.
50 * @param sb StringBuilder to use
51 * @param key Key to append.
52 * @param value Value to append.
53 * @param separator Value to use between key and value.
54 * @param keyValueSeparator Value to use between key/value sets.
55 * @return Passed <code>sb</code> populated with key/value.
56 */
57 public static StringBuilder appendKeyValue(final StringBuilder sb,
58 final String key, final Object value, final String separator,
59 final String keyValueSeparator) {
60 if (sb.length() > 0) {
61 sb.append(keyValueSeparator);
62 }
63 return sb.append(key).append(separator).append(value);
64 }
65
66 /**
67 * Given a PTR string generated via reverse DNS lookup, return everything
68 * except the trailing period. Example for host.example.com., return
69 * host.example.com
70 * @param dnPtr a domain name pointer (PTR) string.
71 * @return Sanitized hostname with last period stripped off.
72 *
73 */
74 public static String domainNamePointerToHostName(String dnPtr) {
75 if (dnPtr == null)
76 return null;
77 return dnPtr.endsWith(".") ? dnPtr.substring(0, dnPtr.length()-1) : dnPtr;
78 }
79
80 /**
81 * Null-safe length check.
82 * @param input
83 * @return true if null or length==0
84 */
85 public static boolean isEmpty(String input) {
86 return input == null || input.length() == 0;
87 }
88
89 /**
90 * Push the input string to the right by appending a character before it, usually a space.
91 * @param input the string to pad
92 * @param padding the character to repeat to the left of the input string
93 * @param length the desired total length including the padding
94 * @return padding characters + input
95 */
96 public static String padFront(String input, char padding, int length) {
97 if (input.length() > length) {
98 throw new IllegalArgumentException("input \"" + input + "\" longer than maxLength=" + length);
99 }
100 int numPaddingCharacters = length - input.length();
101 return repeat(padding, numPaddingCharacters) + input;
102 }
103
104 /**
105 * @param c repeat this character
106 * @param reapeatFor the length of the output String
107 * @return c, repeated repeatFor times
108 */
109 public static String repeat(char c, int reapeatFor) {
110 StringBuilder sb = new StringBuilder();
111 for (int i = 0; i < reapeatFor; ++i) {
112 sb.append(c);
113 }
114 return sb.toString();
115 }
116 }