Java实现字符串反转

public class Reverse {
	public static String reverse1(String str) {
		if (str == null || str.length() <= 1)
			return str;
		return new StringBuilder(str).reverse().toString();
	}
	
	public static String reverse2(String str) {
		if (str == null || str.length() <= 1)
			return str;
		return reverse2(str.substring(1)) + str.charAt(0);
	}
	
	public static String reverse3(String str) {
		if (str == null || str.length() <= 1)
			return str;
		char[] ca = new char[str.length()];
		for (int i = 0; i < str.length(); i++) {
			ca[i] = str.charAt(str.length() - i - 1);
		}
		return new String(ca);
	}
	
	public static void main(String[] args) {
		String s = "hello world";
		
		System.out.println(reverse1(s));
		System.out.println(reverse2(s));
		System.out.println(reverse3(s));
	}
}