java 我如何声明一个空的 int
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How can I declare an empty int
提问by Zablah
I want to declare an empty intlike you would do with a String: String userName ="";I need an empty int because I want to select a (random) picture from an array:
我想像int使用 String 一样声明一个空的： String userName ="";我需要一个空的 int 因为我想从一个数组中选择一个（随机）图片：
public int[] mBackground = {
R.drawable.heart,
R.drawable.cane,
R.drawable.watch
};
This is the code I use to get a random picture from the array:
这是我用来从数组中获取随机图片的代码：
public int getBackground(){
int background = "";
Random generate = new Random();
int randomNumber = generate.nextInt(mBackground.length);
background = mBackground[randomNumber];
return background;
}
采纳答案by Fred
I don't understand your question. Why do you need to initialize it? You don't even need the variable.
我不明白你的问题。为什么需要初始化呢？你甚至不需要变量。
This code works as you want
此代码按您的需要工作
public int getBackground(){
Random generate = new Random();
int randomNumber = generate.nextInt(mBackground.length);
return mBackground[randomNumber];
}
However, if you want to have a variable you can do
但是，如果你想要一个变量，你可以这样做
public int getBackground(){
Random generate = new Random();
int randomNumber = generate.nextInt(mBackground.length);
int background = mBackground[randomNumber];
return background;
}
回答by gknicker
If you must assign your int backgroundvariable a default value for some reason, -1is often workable. You cannot assign an intvariable to anything other than an integer value (""is a Stringso won't work).
如果int background出于某种原因必须为变量分配一个默认值，-1这通常是可行的。您不能将分配int变量不是一个整数值以外的任何（""是String这样将无法正常工作）。
int background = -1;
// ...
if (background < 0) {
// handle invalid value, perhaps assign a default
}
If you need your variable to point to "nothing", consider using the boxed type Integer, which you can initialize to null.
如果您需要变量指向“无”，请考虑使用盒装类型Integer，您可以将其初始化为null。
Integer background = null; // will throw NullPointerException if unboxed to int
Otherwise, don't declare the variable until you're ready to assign it. That way you don't have to give it a pointless initial value.
否则，在准备分配变量之前不要声明变量。这样你就不必给它一个毫无意义的初始值。
int background = mBackground[randomNumber];
Or you could just return the value straight from your method instead of assigning it to an intermediate variable.
或者您可以直接从您的方法中返回值，而不是将其分配给中间变量。
return mBackground[randomNumber];
You actually don't have to initialize a local variable at all when you declare it. This is perfectly acceptable.
当你声明一个局部变量时，你实际上根本不需要初始化它。这是完全可以接受的。
int background;
However, you must assign a value before you can use it.
但是，您必须先分配一个值，然后才能使用它。
Here's the shortest statement of your method's intention.
这是您的方法意图的最短陈述。
public int getBackground(){
return mBackground[new Random().nextInt(mBackground.length)];
}
回答by James S
There is no such thing as an empty int in the context you have given, an empty string is a String containing a sequence of 0 length. int is a primitive data type and can't take any value outside the parameters of either a signed or unsigned 32-bit integer unless you want to declare as an Integer boxed Object in which case you can declare it as null.
在您给出的上下文中没有空 int 之类的东西，空字符串是包含长度为 0 的序列的字符串。int 是一种原始数据类型，不能在有符号或无符号 32 位整数的参数之外取任何值，除非您想声明为整数盒装对象，在这种情况下，您可以将其声明为 null。
For a method as simple as selecting a random value from an array you may as well just use a one-liner.
对于从数组中选择随机值这样简单的方法，您也可以只使用单行。
public int getBackground(){
return mBackground[new Random().nextInt(mBackground.length)];
}
