1 import org.junit.Test;
 2 
 3 public class StringtoChar {
 4     @Test
 5     public  void main(){
 6         String str ="hello  world!";
 7 //        String str1 = str.trim();//trim()只是去掉首尾空格
 8         String str1 = str.replace(" ", "");
 9         //1:
10         System.out.println(str1);
11         System.out.println("第一種方法：");
 
12         for (int i = str1.length()-1; i >=0 ; i--) {
13             char ch=str1.charAt(i);
14             System.out.print(ch);
15         }
16         
17     }
18 }

 1 import org.junit.Test;
 2 
 3 public class StringtoChar {
 4     @Test
 5     public  void main(){
 6         String str ="hello  world!";
 
 7 //        String str1 = str.trim();//trim()只是去掉首尾空格
 8         String str1 = str.replace(" ", "");
 9         
10         //2:
11         System.out.println();
12         System.out.println("第二種方法：");
13         char[] a = str1.toCharArray();
14         for (int i = str1.length()-1; i >=0 ; i--) {
15             System.out.print(a[i]);
 
16         }
17 
18     }
19 }

 1 import org.junit.Test;
 2 
 3 public class StringtoChar {
 4     @Test
 5     public  void main(){
 6         System.out.println("第三種方法：");
 7         StringBuffer s = new StringBuffer(" hello   world !");
 8         System.out.println("原始字符串"+s);
 9         s.reverse();//字符串倒序
10         System.out.println("倒序字符串"+s);
11         String ss =s.toString();
12         String ss2 = ss.trim();//trim()只是去掉首尾空格
13         String ss3 = ss.replace(" ","");
14         System.out.println(ss2);
15         System.out.println(ss3);
16     }
17 }

帶空格字符串的倒序輸出