9）用StringBuilder类把上面的字符串数组重新组装成一个StringBuilder对象【调用.append()方法】，打印输出StringBuilder对象的字符串；

代码如下：

String[] strArray = {"Java", "is", "a", "popular", "programming", "language"};
StringBuilder sb = new StringBuilder();
for (String str : strArray) {
    sb.append(str).append(" ");
}
System.out.println(sb.toString());

输出结果为：

Java is a popular programming language