Here you can find the source of toUpperCase(String str)
public static String toUpperCase(String str)
//package com.java2s; /**/* w w w . j a v a 2 s . c o m*/ * Copyright 2013 ?????? * * 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. */ public class Main { public static final String EMPTY = ""; public static String toUpperCase(String str) { if (str == null) { return null; } return str.toUpperCase(); } public static String toUpperCase(String str, int beginIndex, int endIndex) { if (str == null) { return null; } StringBuilder sb = new StringBuilder(); if (beginIndex < 0) { beginIndex = 0; } if (endIndex > str.length()) { endIndex = str.length(); } if (beginIndex > 0) { sb.append(str.substring(0, beginIndex)); } sb.append(str.substring(beginIndex, endIndex).toUpperCase()); if (endIndex < str.length()) { sb.append(str.substring(endIndex)); } return sb.toString(); } public static String substring(String str, int beginIndex) { if (str == null) { return null; } if (beginIndex < 0) { return EMPTY; } if (beginIndex > str.length()) { return EMPTY; } return str.substring(beginIndex); } public static String substring(String str, int beginIndex, int endIndex) { if (str == null) { return null; } if (beginIndex < 0 || endIndex < 0) { return EMPTY; } if (endIndex > str.length()) { endIndex = str.length(); } if (beginIndex > endIndex || beginIndex > str.length()) { return EMPTY; } return str.substring(beginIndex, endIndex); } }