我们可以在不定义列数的情况下定义 new Object[3][] 吗? [英] Can we define new Object[3][] without defining number of columns?

问题描述

有人可以帮我理解下面的代码吗?我是 Java 新手，我正在尝试学习 Objects[].此代码编译但 retval 不返回任何内容?

Can someone please help me understand the following code? I'm new to java, I'm trying to learn Objects[]. This code compiles but retval does not return anything?

1. 我在网上做了很多搜索，但找不到为什么 Object[3][] 编译并且不抱怨?

1. I've done a lot of search online but can't find why is Object[3][] compiles and does not complain?

下面的代码是什么意思?
(新对象[1])[0] = tt;

What does the following code mean?
(new Object[1])[0] = tt;

如何才能retval[0] = new Object[1];"如果 Object 是二维数组则编译.

How can "retval[0] = new Object[1];" compile if Object is two dimensional array.

package Package1;
import org.testng.annotations.Test;
public class Test1
{

@Test
public void NewTest()
{
    Object[][] retval = new Object[3][];

    int i = 0;
    String methodName = "NewTest";
    String className = this.getClass().toString();
    String desc = "This is a test";

    TestTest tt = new TestTest(methodName, className, desc); 
    System.out.println(tt.str1);
    System.out.println(tt.str2);
    System.out.println(tt.str3);

    (new Object[1])[0] =    tt; 
        retval[0] = new Object[1];    
        retval[1] = new Object[1];
        retval[2] = new Object[1];
        System.out.println("object 0 = " + retval[0]);
        System.out.println("object 1 = " + retval[1]);
        System.out.println("object 2 = " + retval[2]);
}     

}

package Package1;

public class TestTest 
{

String str1 = "apple";
String str2 = "grape";
String str3 = "orange";


public TestTest(String a, String b, String c)
{
    this.str1 = a;
    this.str2 = b;
    this.str3 = c;
}

}

推荐答案

1. 请记住，创建一个二维数组只是创建一个数组数组.二维数组中数组的长度与保存它们的数组无关.

1. Remember that creating a 2D array is just making an array of arrays. The length of the arrays within the 2D array is no concern of the array holding them.

 Object[][] r = new Object[3][];
 Object[] j = new Object[2];

 r[0] = j;

在这个例子中，我们创建了一个可以容纳 3 个数组的二维数组 'r'.然后我们定义一个可以容纳 2 个对象的一维数组 'j'.然后我们将'r'的第一个数组设置为'j'.

In this example, we create a 2D array 'r' that can hold 3 arrays. Then we define a 1D array 'j' that can hold 2 Objects. Then we set the first array of 'r' to be 'j'.

但是，如果您希望二维数组中的数组长度为特定值；您必须为其分配一个值.

However, if you want the length of the arrays within your 2D array to be a specific value; you will have to assign it a value.

请记住，无论数组的维数如何，引用数组中的索引都是相同的.然而，数组包含的内容会有所不同.

Remember that referring to an index in an array is the same no matter the dimension of the array. What the array contains will be different however.

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