使用 String.replaceAll() 方法

通过正则表达式来查找字符串前面的空格。
^表示以xx（这里是\s 表示空格）开头。

String regex = "^\s+";

String oroirnalString1 = "   onitroad.com"; 
String oroirnalString2 = "   onitroad.com   "; 
String trimmedString1 = oroirnalString1.replaceAll(regex, "");
String trimmedString2 = oroirnalString2.replaceAll(regex, "");
System.out.println(trimmedString1);
System.out.println(trimmedString2);

使用String.replaceFirst() 方法

替换第1个匹配项：

String regex = "^\s+";

String oroirnalString1 = "   onitroad.com";	 
String oroirnalString2 = "   onitroad.com   "; 
String trimmedString1 = oroirnalString1.replaceFirst(regex, "");
String trimmedString2 = oroirnalString2.replaceFirst(regex, "");
System.out.println(trimmedString1);
System.out.println(trimmedString2);

使用 String.trim() 方法去除前后空格

String oroirnalString1 = "   onitroad.com";  
String oroirnalString2 = "   onitroad.com   ";  
String trimmedString1 = oroirnalString1.trim();
String trimmedString2 = oroirnalString2.trim();
System.out.println(trimmedString1);
System.out.println(trimmedString2);