java_去除字符串中的空格的几种方法

/**
*
*/
package 作业0919;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class 去除空格 {

public static void main(String[] args) {
String string = "aa bb     cc   dd";
String string1 = "";

// 方法一:
String string2 = string.replaceAll(" ", "");
System.out.println(string2);

// 方法二:
for (int i = 0; i < string.length(); i++) {
if (!String.valueOf(string.charAt(i)).equals(" ")) {
string1 += string.charAt(i);
}

}
System.out.println(string1);

// 方法三:
String regex = "\\s";
String[] string3 = string.split(regex);
String string4 = "";
for (int i = 0; i < string3.length; i++) {
string4 += string3[i];

}
System.out.println(string4);

System.out.println("************");

Matcher matcher = Pattern.compile(regex).matcher(string);
while (matcher.find()) {
System.out.println(matcher.group());

}

}
}