Hans Boehm | 24c91ed | 2016-06-30 18:53:44 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2016 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.android.calculator2; |
| 18 | |
| 19 | /** |
| 20 | * Some helpful methods operating on strings. |
| 21 | */ |
| 22 | |
| 23 | public class StringUtils { |
| 24 | |
| 25 | /** |
| 26 | * Return a string with n copies of c. |
| 27 | */ |
| 28 | public static String repeat(char c, int n) { |
| 29 | final StringBuilder result = new StringBuilder(); |
| 30 | for (int i = 0; i < n; ++i) { |
| 31 | result.append(c); |
| 32 | } |
| 33 | return result.toString(); |
| 34 | } |
| 35 | |
| 36 | /** |
| 37 | * Return a copy of the supplied string with commas added every three digits. |
| 38 | * The substring indicated by the supplied range is assumed to contain only |
| 39 | * a whole number, with no decimal point. |
| 40 | * Inserting a digit separator every 3 digits appears to be |
| 41 | * at least somewhat acceptable, though not necessarily preferred, everywhere. |
| 42 | * The grouping separator in the result is NOT localized. |
| 43 | */ |
| 44 | public static String addCommas(String s, int begin, int end) { |
| 45 | // Resist the temptation to use Java's NumberFormat, which converts to long or double |
| 46 | // and hence doesn't handle very large numbers. |
| 47 | StringBuilder result = new StringBuilder(); |
| 48 | int current = begin; |
| 49 | while (current < end && (s.charAt(current) == '-' || s.charAt(current) == ' ')) { |
| 50 | ++current; |
| 51 | } |
| 52 | result.append(s, begin, current); |
| 53 | while (current < end) { |
| 54 | result.append(s.charAt(current)); |
| 55 | ++current; |
| 56 | if ((end - current) % 3 == 0 && end != current) { |
| 57 | result.append(','); |
| 58 | } |
| 59 | } |
| 60 | return result.toString(); |
| 61 | } |
| 62 | |
| 63 | /** |
| 64 | * Ignoring all occurrences of c in both strings, check whether old is a prefix of new. |
| 65 | * If so, return the remaining subsequence of whole. If not, return null. |
| 66 | */ |
| 67 | public static CharSequence getExtensionIgnoring(CharSequence whole, CharSequence prefix, |
| 68 | char c) { |
| 69 | int wIndex = 0; |
| 70 | int pIndex = 0; |
| 71 | final int wLen = whole.length(); |
| 72 | final int pLen = prefix.length(); |
| 73 | while (true) { |
| 74 | while (pIndex < pLen && prefix.charAt(pIndex) == c) { |
| 75 | ++pIndex; |
| 76 | } |
| 77 | while (wIndex < wLen && whole.charAt(wIndex) == c) { |
| 78 | ++wIndex; |
| 79 | } |
| 80 | if (pIndex == pLen) { |
| 81 | break; |
| 82 | } |
| 83 | if (wIndex == wLen || whole.charAt(wIndex) != prefix.charAt(pIndex) ) { |
| 84 | return null; |
| 85 | } |
| 86 | ++pIndex; |
| 87 | ++wIndex; |
| 88 | } |
| 89 | while (wIndex < wLen && whole.charAt(wIndex) == c) { |
| 90 | ++wIndex; |
| 91 | } |
| 92 | return whole.subSequence(wIndex, wLen); |
| 93 | } |
| 94 | } |