字符串去除多余空格

public class StringTrim {
	public static void main(String[] args) {
		String s = " ni   hao luffy !     !";
		String s2 = "12niasdnk123asd3123dasd";
		System.out.println(fun2(s));
	}
	
	// 去掉字符串多余的空格
	public static String fun1(String s) {
	//获取两个空格的索引
		int index = s.indexOf("  ");
		while (index != -1) {
		//字符串拼接
			s = s.substring(0, index).concat(s.substring(index + 1));
			index = s.indexOf("  ");
		}
		return s;
	}

	// 去掉字符串多余的空格
	public static String fun2(String s) {
		return s.replaceAll("\\s+", " ");
	}

	// 去掉字符串的数字
	public static String fun3(String s) {
		return s.replaceAll("\\d", "");
	}

	// 去掉所有空格
	public static String fun4(String s) {
		return s.replace(" ", "");
		//return s.replaceAll("\\s+", "");
	}

}