字符串反轉實現

@(技術筆記)[java|算法]

字符串反轉實現

• jdk自帶方式
• for循環
• 遞歸

package base.views.json;

/**
 * Created by xiaofeng.song on 2014/10/11.
 */
public class TestStringUtils {

    public static void main(String args[]) {
        System.out.println(reverseFor("你們好"));
        System.out.println(reverseJdk("你們好嗎？"));
        System.out.println(reverseRecursion("你們好嗎？么么噠！"));
    }

    public static String reverseJdk(String str) {
        if (str == null || "".equals(str)) {
            return str;
        }
        return new StringBuffer(str).reverse().toString();
    }

    public static String reverseFor(String str) {
        if (str == null || "".equals(str)) {
            return str;
        }
        StringBuffer sb = new StringBuffer();
        for (int i = str.length() - 1; i >= 0; i--) {
            sb.append(str.charAt(i));
        }
        return sb.toString();
    }

    public static String reverseRecursion(String str) {
        if (str == null || "".equals(str)) {
            return str;
        }
        StringBuffer sb = new StringBuffer();
        return _reverse(sb, str, str.length());
    }

    private static String _reverse(StringBuffer sb, String str, int length) {
        if (length > 0) {
            sb.append(str.charAt(length - 1));
            length--;
//            System.out.println(sb.toString());
            String st = _reverse(sb, str, length);
            return st;
        } else {
            return sb.toString();
        }
    }
}