对于字符串处理问题,笔试中我们经常会遇到直接或间接的需要将字符串翻转(颠倒)的问题,下面介绍(但不限于)几种方法:
方法1:使用toCharArray( )方法,然后反向赋值
import java.util.*; public class Test5{ public static void main(String[] args){ Scanner sc = new Scanner(System.in); while(sc.hasNext()){ char[] c1 = sc.next().toCharArray(); int len = c1.length; char[] c2 = new char[len]; for(int i = 0; i < len; i ++){ c2[i] = c1[len-1-i]; } String res = new String(c2); System.out.println(res); } } }
方法2:使用StringBuilder类的reverse( )方法
import java.util.Scanner; public class Main{ public static void main(String[] args){ Scanner sc = new Scanner(System.in); while(sc.hasNext()){ System.out.println(new StringBuilder(sc.next()).reverse()); } } }
方法3:若只考虑输出,不考虑返回
import java.util.Scanner; public class Main{ public static void main(String[] args){ Scanner sc = new Scanner(System.in); while(sc.hasNext()){ String s = sc.next(); for(int i = s.length()-1; i >= 0; i--) System.out.print(s.charAt(i)); } } }
方法4:使用collections的静态方法reverse( )
import java.util.*; public class Test5{ public static void main(String[] args){ Scanner sc = new Scanner(System.in); while(sc.hasNext()){ /* char[] c = sc.next().toCharArray(); List<Character> list = new ArrayList<Character>(); for(int i =0;i<c.length;i++) list.add(c[i]); Collections.reverse(list); for(Character cha:list) System.out.print(cha); */ String[] s = sc.nextLine().split(""); List<String> list = Arrays.asList(s); Collections.reverse(list); for(String s1:list) System.out.print(s1); } } }