数字输入字符串“trim”和“replaceAll”不能去掉最后一个空格

Question

I want to remove all spaces in a string of numeric types, I used the function such as trim() , replaceall(" ", "") , but the last space always goes to off.

code:

String str = " 13554912187 ";
//String str2 = str.replaceAll(" ", "");
String str2 = str.trim();
System.out.println(str);
System.out.println(str.length());
System.out.println(str2);
System.out.println(str2.length());

I want to know why.

Answer 1

Make sure the trailing space is actually considered whitespace by String.trim() - only characters with code less than or equal to \ are considered whitespace - see String.trim() documentation .

Some possible ways to check this:

• Copy the leading space and replace the trailing space with it (assuming the leading space works OK)
• Open the file this input comes from in a hex editor
• Debug the Java application and see what value is stored in the String instance for that last space

Answer 2

 String str = " 13554912187 ";

Trim leading and trailing blanks

    str.trim(); -> "13554912187"

For left trim:

    str.replaceAll("^\\s+", ""); -> "13554912187 "

For right trim:

    str.replaceAll("\\s+$", ""); -> " 13554912187"

Visual proof for the incredulous

Answer 3

String str2 = str.trim();

trim() method remove space before and after the word.

like

String s=" 45654 65 ";
System.out.println(s.startsWith(" "));
System.out.println(s.endsWith(" "));

s=s.trim();
System.out.println(s.startsWith(" "));
System.out.println(s.endsWith(" "));

output:

true
true
false
false