java实现带空格字符串的倒序输出

import org.junit.Test;

public class StringtoChar {
    @Test
    public  void main(){
        String str ="hello  world!";
//        String str1 = str.trim();//trim()只是去掉首尾空格
        String str1 = str.replace(" ", "");
        //1:
        System.out.println(str1);
        System.out.println("第一种方法：");
        for (int i = str1.length()-1; i >=0 ; i--) {
            char ch=str1.charAt(i);
            System.out.print(ch);
        }
        
    }
}

import org.junit.Test;

public class StringtoChar {
    @Test
    public  void main(){
        String str ="hello  world!";
//        String str1 = str.trim();//trim()只是去掉首尾空格
        String str1 = str.replace(" ", "");
        
        //2:
        System.out.println();
        System.out.println("第二种方法：");
        char[] a = str1.toCharArray();
        for (int i = str1.length()-1; i >=0 ; i--) {
            System.out.print(a[i]);
        }

    }
}

import org.junit.Test;

public class StringtoChar {
    @Test
    public  void main(){
        System.out.println("第三种方法：");
        StringBuffer s = new StringBuffer(" hello   world !");
        System.out.println("原始字符串"+s);
        s.reverse();//字符串倒序
        System.out.println("倒序字符串"+s);
        String ss =s.toString();
        String ss2 = ss.trim();//trim()只是去掉首尾空格
        String ss3 = ss.replace(" ","");
        System.out.println(ss2);
        System.out.println(ss3);
    }
}