java-判断字符串是否由纯数字组成

上代码：

    static boolean isNum(String s) {
		char[] ch = s.toCharArray();
		for (char c : ch) {
			if (!(c > '0' && c <= '9')) {
				return false;
			}
		}
		return true;
	}

	@Test
	public void test02() {
		System.out.println("***************");
		String s1 = "123456";
		System.out.println(isNum(s1));//true
		String s2 = "1234as65";
		System.out.println(isNum(s2));//false
	}