java：原始数组——它们是否已初始化？
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java: primitive arrays -- are they initialized?
提问by Jason S
If I use a statement in my code like
如果我在我的代码中使用像
int[] a = new int[42];
Will it initialize the array to anything in particular? (e.g. 0) I seem to remember this is documented somewhere but I am not sure what to search for.
它会将数组初始化为任何特别的东西吗？（例如 0）我似乎记得这是在某处记录的，但我不确定要搜索什么。
采纳答案by p00ya
At 15.10 Array Creation Expressionsthe JLS says
JLS在15.10 Array Creation Expressions说
[...] a single-dimensional array is created of the specified length, and each component of the array is initialized to its default value
[...] 创建指定长度的一维数组，并将数组的每个组件初始化为其默认值
and at 4.12.5 Initial Values of Variablesit says:
在4.12.5 Initial Values of Variables它说：
For type
int, the default value is zero, that is,0.
对于 type
int，默认值为零，即0。
回答by Bozhidar Batsov
When created, arrays are automatically initialized with the default value of their type - in your case that would be 0. The default is falsefor booleanand nullfor all reference types.
创建时，数组会自动使用其类型的默认值进行初始化 - 在您的情况下为0. 默认值是false为boolean与null所有引用类型。
回答by Haldean Brown
All elements in the array are initialized to zero. I haven't been able to find evidence of that in the Java documentation but I just ran this to confirm:
数组中的所有元素都初始化为零。我一直无法在 Java 文档中找到证据，但我只是运行它来确认：
int[] arrayTest = new int[10];
System.out.println(arrayTest[5]) // prints zero
回答by OscarRyz
The array would be initialized with 42 0s
数组将用 42 个 0 初始化
For other data types it would be initialized with the default value ie.
对于其他数据类型，它将使用默认值进行初始化，即。
new boolean[42]; // would have 42 falses
new double[42]; // would have 42 0.0 ( or 0.0D )
new float[42]; // 42 0.0fs
new long[42]; // 42 0Ls
And so on.
等等。
For objects in general it would be null:
对于一般的对象，它将为空：
String [] sa = new String[42]; // 42 nulls
Date [] da = new Date[42]; // 42 nulls
