[英]Java : Best way to pass int by reference
I have a parsing function that parses an encoded length from a byte buffer, it returns the parsed length as an int, and takes an index into the buffer as an integer arg. 我有一个解析函数,它解析来自字节缓冲区的编码长度,它将解析的长度作为int返回,并将索引作为整数arg作为缓冲区。 I want the function to update the index according to what it's parsed, ie want to pass that index by reference. 我希望函数根据它的解析来更新索引,即希望通过引用传递该索引。 In C I'd just pass an int *
. 在C中,我只传递一个int *
。 What's the cleanest way to do this in Java? 在Java中最干净的方法是什么? I'm currently looking at passing the index arg. 我目前正在考虑传递索引arg。 as an int[]
, but it's a bit ugly. 作为int[]
,但它有点难看。
You can try using org.apache.commons.lang.mutable.MutableInt
from Apache Commons library. 您可以尝试使用Apache Commons库中的org.apache.commons.lang.mutable.MutableInt
。 There is no direct way of doing this in the language itself. 在语言本身没有直接的方法。
This isn't possible in Java. 这在Java中是不可能的。 As you've suggested one way is to pass an int[]
. 正如您所建议的那样,一种方法是传递int[]
。 Another would be do have a little class eg IntHolder
that wrapped an int
. 另一个会有一个小类,例如包含int
IntHolder
。
You cannot pass arguments by reference in Java. 您不能通过Java中的引用传递参数。
What you can do is wrap your integer value in a mutable object. 你可以做的是将整数值包装在一个可变对象中。 Using Apache Commons' MutableInt
is a good option. 使用Apache Commons的MutableInt
是一个不错的选择。 Another, slightly more obfuscated way, is to use an int[]
like you suggested. 另一种稍微混淆的方式是使用你建议的int[]
。 I wouldn't use it as it is unclear as to why you are wrapping an int
in a single-celled array. 我不会使用它,因为不清楚为什么要在单细胞阵列中包装int
。
Note that java.lang.Integer
is immutable. 请注意, java.lang.Integer
是不可变的。
Wrap the byte buffer and index into a ByteBuffer object. 将字节缓冲区和索引包装到ByteBuffer对象中。 A ByteBuffer encapsulates the concept of a buffer+position and allows you to read and write from the indexed position, which it updates as you go along. ByteBuffer封装了缓冲区+位置的概念,允许您从索引位置读取和写入,随着时间的推移,它会更新。
您可以使用java.util.concurrent.atomic.AtomicInteger
。
You can design new class like this: 你可以设计这样的新类:
public class Inte{
public int x=0;
}
later you can create object of this class : 以后你可以创建这个类的对象:
Inte inte=new Inte();
then you can pass inte
as argument where you want to pass an integer variable: 然后你可以将inte
作为参数传递给你想传递整数变量的地方:
public void function(Inte inte) {
some code
}
so for update the integer value: 所以更新整数值:
inte.x=value;
for getting value: 获得价值:
Variable=inte.x;
You can create a Reference class to wrap primitives: 您可以创建一个Reference类来包装基元:
public class Ref<T>
{
public T Value;
public Ref(T value)
{
Value = value;
}
}
Then you can create functions that take a Reference as a parameters: 然后,您可以创建将Reference作为参数的函数:
public class Utils
{
public static <T> void Swap(Ref<T> t1, Ref<T> t2)
{
T temp = t1.Value;
t1.Value = t2.Value;
t2.Value = temp;
}
}
Usage: 用法:
Ref<Integer> x = 2;
Ref<Integer> y = 9;
Utils.Swap(x, y);
System.out.println("x is now equal to " + x.Value + " and y is now equal to " + y.Value";
// Will print: x is now equal to 9 and y is now equal to 2
Hope this helps. 希望这可以帮助。
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