The problem of removing spaces from strings

Have a headache , I can't figure out what this space is , character string str=“123　　48 454878”, Want to get only numbers , Usage method str.replace(" “,”"); The result is “123　　48454878”, Aren't those two lumps in front of you blank spaces ？

In regular expressions ,\s Matches any whitespace characters , Including Spaces 、 tabs 、 Page breaks and so on . Equivalent to [ \f\n\r\t\v]. But this space doesn't match \s. as follows ：

String str = "123　　48 454878";
System.out.println(str.replaceAll("\\s", ""));// The result is 123　　48454878, It's just removed 8 and 4 Space between 

Only later did I know , Spaces and others ：
1. Continuous space \u00A0, Mainly used in office in , Let a word not wrap at the end , Shortcut key ctrl+shift+space ;
2. Half space ( English symbols )\u0020, Commonly used in code ;
3. Full space ( Chinese symbols )\u3000, Use... In Chinese articles .

Use Transformation tool , Copy the space above into , The result is converted to \u3000, So modify the code ：

String str = "123　　48 454878";
System.out.println(str.replaceAll("\\u3000", "").replaceAll("\\s", ""));// The result is 12348454878