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/*
* Copyright (C) 2016 The Android Open Source Project
*
* 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 com.android.calculator2;
/**
* Some helpful methods operating on strings.
*/
public class StringUtils {
/**
* Return a string with n copies of c.
*/
public static String repeat(char c, int n) {
final StringBuilder result = new StringBuilder();
for (int i = 0; i < n; ++i) {
result.append(c);
}
return result.toString();
}
/**
* Return a copy of the supplied string with commas added every three digits.
* The substring indicated by the supplied range is assumed to contain only
* a whole number, with no decimal point.
* Inserting a digit separator every 3 digits appears to be
* at least somewhat acceptable, though not necessarily preferred, everywhere.
* The grouping separator in the result is NOT localized.
*/
public static String addCommas(String s, int begin, int end) {
// Resist the temptation to use Java's NumberFormat, which converts to long or double
// and hence doesn't handle very large numbers.
StringBuilder result = new StringBuilder();
int current = begin;
while (current < end && (s.charAt(current) == '-' || s.charAt(current) == ' ')) {
++current;
}
result.append(s, begin, current);
while (current < end) {
result.append(s.charAt(current));
++current;
if ((end - current) % 3 == 0 && end != current) {
result.append(',');
}
}
return result.toString();
}
/**
* Ignoring all occurrences of c in both strings, check whether old is a prefix of new.
* If so, return the remaining subsequence of whole. If not, return null.
*/
public static CharSequence getExtensionIgnoring(CharSequence whole, CharSequence prefix,
char c) {
int wIndex = 0;
int pIndex = 0;
final int wLen = whole.length();
final int pLen = prefix.length();
while (true) {
while (pIndex < pLen && prefix.charAt(pIndex) == c) {
++pIndex;
}
while (wIndex < wLen && whole.charAt(wIndex) == c) {
++wIndex;
}
if (pIndex == pLen) {
break;
}
if (wIndex == wLen || whole.charAt(wIndex) != prefix.charAt(pIndex) ) {
return null;
}
++pIndex;
++wIndex;
}
while (wIndex < wLen && whole.charAt(wIndex) == c) {
++wIndex;
}
return whole.subSequence(wIndex, wLen);
}
}
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