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 final class Strings {
28 public static final String DEFAULT_SEPARATOR = "=";
29 public static final String DEFAULT_KEYVALUE_SEPARATOR = ", ";
30
31 private Strings() {
32 }
33
34 /**
35 * Append to a StringBuilder a key/value.
36 * Uses default separators.
37 * @param sb StringBuilder to use
38 * @param key Key to append.
39 * @param value Value to append.
40 * @return Passed <code>sb</code> populated with key/value.
41 */
42 public static StringBuilder appendKeyValue(final StringBuilder sb,
43 final String key, final Object value) {
44 return appendKeyValue(sb, key, value, DEFAULT_SEPARATOR,
45 DEFAULT_KEYVALUE_SEPARATOR);
46 }
47
48 /**
49 * Append to a StringBuilder a key/value.
50 * Uses default separators.
51 * @param sb StringBuilder to use
52 * @param key Key to append.
53 * @param value Value to append.
54 * @param separator Value to use between key and value.
55 * @param keyValueSeparator Value to use between key/value sets.
56 * @return Passed <code>sb</code> populated with key/value.
57 */
58 public static StringBuilder appendKeyValue(final StringBuilder sb,
59 final String key, final Object value, final String separator,
60 final String keyValueSeparator) {
61 if (sb.length() > 0) {
62 sb.append(keyValueSeparator);
63 }
64 return sb.append(key).append(separator).append(value);
65 }
66
67 /**
68 * Given a PTR string generated via reverse DNS lookup, return everything
69 * except the trailing period. Example for host.example.com., return
70 * host.example.com
71 * @param dnPtr a domain name pointer (PTR) string.
72 * @return Sanitized hostname with last period stripped off.
73 */
74 public static String domainNamePointerToHostName(String dnPtr) {
75 if (dnPtr == null) {
76 return null;
77 }
78
79 return dnPtr.endsWith(".") ? dnPtr.substring(0, dnPtr.length()-1) : dnPtr;
80 }
81
82 /**
83 * Null-safe length check.
84 * @param input the {@link String} to do the null-safe length check for
85 * @return true if null or length==0
86 */
87 public static boolean isEmpty(String input) {
88 return input == null || input.length() == 0;
89 }
90
91 /**
92 * Push the input string to the right by appending a character before it, usually a space.
93 * @param input the string to pad
94 * @param padding the character to repeat to the left of the input string
95 * @param length the desired total length including the padding
96 * @return padding characters + input
97 */
98 public static String padFront(String input, char padding, int length) {
99 if (input.length() > length) {
100 throw new IllegalArgumentException("input \"" + input + "\" longer than maxLength=" + length);
101 }
102 int numPaddingCharacters = length - input.length();
103 return repeat(padding, numPaddingCharacters) + input;
104 }
105
106 /**
107 * @param c repeat this character
108 * @param reapeatFor the length of the output String
109 * @return c, repeated repeatFor times
110 */
111 public static String repeat(char c, int reapeatFor) {
112 StringBuilder sb = new StringBuilder();
113 for (int i = 0; i < reapeatFor; ++i) {
114 sb.append(c);
115 }
116 return sb.toString();
117 }
118 }