CODEWITHSUNDEEP
javaargumentsvariadic-functions
pt123
pt123

Reputation: 2166

Variable Arguments of Object passing in array inconsistency

I wrote a function that would take variable arguments as object.

When I passed in an array of ints of size 1 eg {9}, it treated args[0] as and int array[] than an int so the valueOf did not produce 9.

But If passed in and array of 2 or more ints eg {9,11} then it treated args[0] as 9 and args[1] as 11. Why does it behave differently.

Note it is being written for Android. 

protected String[] whereArgs(Object...args) {
    String[] argsStrings = new String[args.length];
    for (int i = 0; i < args.length; i++) {
        if (args[i] instanceof String){
            argsStrings[i] = (String)args[i];
        } else {
            argsStrings[i] = String.valueOf(args[i]);   
        }
    }
    return argsStrings;
}

EDIT Just had a look again I was actually passing them differently in the two ints scenario, one by one and not in an array, sorry.

Why doesn't it split the method(Object...args) into an array of objects when I pass in an array of ints, like what happens with method(int...args)

So now to get the string value I have to individually cast the type of array eg. for int[], double[]

if (args[0] instanceof int[]){
    argsStrings[0] =  String.valueOf(((int[])args[0])[0]);

Is there a way to write it for any type of object as this causes a crash

argsStrings[0] = String.valueOf(((Object[])args[0])[0]);

java.lang.ClassCastException: int[] cannot be cast to java.lang.Object[]

Upvotes: 3

Views: 1264

Answers (1)

Dev Blanked
Dev Blanked

Reputation: 8865

If you want to pass an array and treat each item as a separate item of the 'args' parameter of your method.. you need to cast your array to an Object[]. e.g: If you pass in your array of integers like below it will do what you want.

whereArgs((Object[])(new Integer[]{1, 2}))

The reason for this is when the source is compiled var-arg methods are actually replaced by an array. all places where the method is being called is converted to an array. If you want to pass an array so that each item becomes a separate argument.. then you need to use the correct array type. in your scenario this will be Object[]. This lets the compiler know that it can leave the method call as it is (without putting the arguments inside a new object[])

Upvotes: 2

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