java生成随机数字和字母组合

public static String getCharAndNumr(int length) {
    String val = "";
    Random random = new Random();
    for (int i = 0; i < length; i++) {
        // 输出字母还是数字
        String charOrNum = (2) % 2 == 0 ? "char" : "num";
	// 字符串
	if ("char".equalsIgnoreCase(charOrNum)) {
	    // 取得大写字母还是小写字母
	    int choice = (2) % 2 == 0 ? 65 : 97;
	    val += (char) (choice + (26));
	} else if ("num".equalsIgnoreCase(charOrNum)) { // 数字
	    val += ((10));
	}
    }
    return val;
}