Java 中的数组初始值设定项中带有尾随逗号的数组 [英] Arrays with trailing commas inside an array initializer in Java

问题描述

数组初始化器可用于在编译时初始化数组.如下所示的带有尾随逗号的初始化程序可以正常编译.

Array initializers can be used to initialize arrays at compile-time. An initializer with trailing commas as shown below compiles fine.

int a[][] = {{1,2,} ,{3,4,} , {5,6,},}; //Trailing commas cause no compiler error

for(int i=0;i<a.length;i++)
{
    for(int j=0;j<2;j++)
    {
        System.out.print(a[i][j]+"\t");
    }
    System.out.println();
}

输出:

1        2        
3        4        
5        6     

<小时>

对于一维数组也是合法的，正如上面的讨论一样.

---

Also legal with one dimension arrays as obvious with the above discussion.

int[] b = {1, 2, 3, 4, 5, 6,}; //A trailing comma causes no compiler error

for(int i=0;i<b.length;i++)
{
    System.out.print(b[i]+"\t");
}

输出:

1        2        3        4        5        6

<小时>

即使以下是合法的语法并且编译良好.

---

Even the following is a legal syntax and compiles fine.

int c[][] = {{,} ,{,} , {,},}; 

编译器应该在逗号 , 之后和之前期望一个常量值(或另一个初始化器).这是怎么编译的?编译器是简单地忽略了这样的逗号还是在这种情况下会发生其他事情?

The compiler should expect a constant value (or another initializer) after and before a comma ,. How is this compiled? Does the compiler simply ignore such commas or something else happens in such a scenario?

推荐答案

尾随逗号被忽略.来自 Java 规范:

The trailing comma is ignored. From the Java specification:

数组初始值设定项中的最后一个表达式之后可能会出现尾随逗号并被忽略.

A trailing comma may appear after the last expression in an array initializer and is ignored.

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