Convert a C# method with "params" modifier to Java

Question

I have a C# method that use "params" modifier for a 2-dimentions array.

/// <summary>
///   Combine vectors horizontally.
/// </summary>
/// 
public static T[] Concatenate<T>(params T[][] vectors)
{
    int size = 0;
    for (int i = 0; i < vectors.Length; i++)
        size += vectors[i].Length;

    T[] r = new T[size];

    int c = 0;
    for (int i = 0; i < vectors.Length; i++)
        for (int j = 0; j < vectors[i].Length; j++)
            r[c++] = vectors[i][j];

    return r;
}

I convert it to Java like this:

{
    int size = 0;
    for (int i = 0; i < vectors.length; i++)
    {
        size += vectors[i].;
    }

    T[] r =(T[]) Array.newInstance(vectors[0][0].getClass(), size);

    int c = 0;
    for (int i = 0; i < vectors.length; i++)
    {
        for (int j = 0; j < vectors[i].length; j++)
        {
                r[c++] = vectors[i][j];
        }
    }

    return r;
}

But it seems to be wrong. Solution doesn't work. Please someone tell me the right way. Thanks a lot.

you have a syntax error on line 4 in your java code. Furthermore, its imcomplete, where is the method declaration? What does "doesn't work" mean? What do you expect to happen, what does happen? — Polygnome, Jun 10 '12 at 13:09
If vectors is of size 0 or vectors[0] if of size 0, your Java code won't work. — Danny Varod, Jun 10 '12 at 13:12
[Stack Overflow is not a code translation service](http://meta.stackexchange.com/a/129362). Please explain the requirements in plain English, not in code in another programming language. — dtb, Jun 10 '12 at 13:29

score 2 · Accepted Answer · edited May 23 '17 at 10:34

2

In Java you use ... instead of params, as is explained here

So you declare your method like this (note the loss of one []):

public static T[] Concatenate<T>(T[]...vectors)

edited May 23 '17 at 10:34

Community

1
1

answered Jun 10 '12 at 13:52

zmbq

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score 0 · Answer 2 · answered Jun 10 '12 at 13:55

0

A couple of suggestions:

Just avoid using arrays and generics together. Thanks to type earasure, they don't play well together. (You don't have that problem on CLR.)
Prefer existing solutions. Guava's Iterables.concat appears to fit the bill here.

answered Jun 10 '12 at 13:55

missingfaktor

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Convert a C# method with "params" modifier to Java

2 Answers2