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);
     }
 }