二维数组可以不初始化列数（第二维）。

下面给出的例子是用两种不同的方式存储二维数组并输出：

1. 这是我们通俗易懂的二维数组存储方法：

String[][] data = new String[][] {{ "youth", "high", "no", "fair", "no" },{ "youth", "high", "no", "excellent", "no" },{ "middle_aged", "high", "no", "fair", "yes" }, };for (String[] s : data) {for (String str : s)System.out.print(str + "\t");System.out.println();}

输出结果：

youth	high	no	fair	no	
youth	high	no	excellent	no	
middle_aged	high	no	fair	yes	

2.这是把第二维定义为字符串数组的方法，输出时需要用到强制字符转换：

Object[] array = new Object[] {new String[] { "age", "income", "student", "credit_rating","buys_computer" },new String[] { "youth", "high", "no", "fair", "no" },new String[] { "youth", "high", "no", "excellent", "no" },};for (int i = 0; i < array.length; i++) {for (int j = 0; j < ((String[]) array[0]).length; j++)System.out.print(<span style="color:#ff0000;">((String[]) array[i])[j]</span> + "\t");System.out.println();}

输出结果跟上面一样。