Java String toUpperCase()
java字符串toUpperCase()方法返回以大写字母表示的字符串。换句话说，它将字符串中的所有字符都转换为大写字母。
toUpperCase()方法的工作方式与toUpperCase(Locale.getDefault())方法相同。它在内部使用默认语言环境。
内部实现
public String toUpperCase(Locale locale) {
if (locale == null) {
throw new NullPointerException();
}
int firstLower;
final int len = value.length;
scan: {
for (firstLower = 0 ; firstLower < len; ) {
int c = (int)value[firstLower];
int srcCount;
if ((c >= Character.MIN_HIGH_SURROGATE) &
&
(c <= Character.MAX_HIGH_SURROGATE)) {
c = codePointAt(firstLower);
srcCount = Character.charCount(c);
}
else {
srcCount = 1;
}
int upperCaseChar = Character.toUpperCaseEx(c);
if ((upperCaseChar == Character.ERROR) || (c != upperCaseChar)) {
break scan;
}
firstLower += srcCount;
}
return this;
}
char[] result = new char[len];
int resultOffset = 0;
System.arraycopy(value, 0, result, 0, firstLower);
String lang = locale.getLanguage();
boolean localeDependent = (lang == "tr" || lang == "az" || lang == "lt");
char[] upperCharArray;
int upperChar;
int srcChar;
int srcCount;
for (int i = firstLower; i < len; i += srcCount) {
srcChar = (int)value[i];
if ((char)srcChar >
= Character.MIN_HIGH_SURROGATE &
&
(char)srcChar <= Character.MAX_HIGH_SURROGATE) {
srcChar = codePointAt(i);
srcCount = Character.charCount(srcChar);
}
else {
srcCount = 1;
}
if (localeDependent) {
upperChar = ConditionalSpecialCasing.toUpperCaseEx(this, i, locale);
}
else {
upperChar = Character.toUpperCaseEx(srcChar);
}
if ((upperChar == Character.ERROR) || (upperChar >= Character.MIN_SUPPLEMENTARY_CODE_POINT)) {
if (upperChar == Character.ERROR) {
if (localeDependent) {
upperCharArray = ConditionalSpecialCasing.toUpperCaseCharArray(this, i, locale);
}
else {
upperCharArray = Character.toUpperCaseCharArray(srcChar);
}
}
else if (srcCount == 2) {
resultOffset += Character.toChars(upperChar, result, i + resultOffset) - srcCount;
continue;
}
else {
upperCharArray = Character.toChars(upperChar);
}
/*
Grow result if needed
*/
int mapLen = upperCharArray.length;
if (mapLen > srcCount) {
char[] result2 = new char[result.length + mapLen - srcCount];
System.arraycopy(result, 0, result2, 0, i + resultOffset);
result = result2;
}
for (int x = 0; x < mapLen; ++x) {
result[i + resultOffset + x] = upperCharArray[x];
}
resultOffset += (mapLen - srcCount);
}
else {
result[i + resultOffset] = (char)upperChar;
}
}
return new String(result, 0, len + resultOffset);
}
签名
toUpperCase()方法有两种变体。字符串toUpperCase()方法的签名或语法如下:
public String toUpperCase()
public String toUpperCase(Locale locale)
toUpperCase()的第二个方法变体，使用给定Locale的规则将所有字符转换为大写。
返回
大写字母的字符串。
Java字符串toUpperCase()方法示例
public class StringUpperExample{
public static void main(String args[]){
String s1="hello string";
String s1upper=s1.toUpperCase();
System.out.println(s1upper);
}
}
输出:
Java字符串toUpperCase(语言环境语言环境)方法示例2
import java.util.Locale;
public class StringUpperExample2 {
public static void main(String[] args) {
String s = "hello string";
String turkish = s.toUpperCase(Locale.forLanguageTag("tr"));
String english = s.toUpperCase(Locale.forLanguageTag("en"));
System.out.println(turkish);
//will print I with dot on upper side System.out.println(english);
}
}
输出:
HELLO STRING
HELLO STRING
