Var-Args
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Jump to navigationJump to search- Var-args are used to defined methods with variable argument lists.
- Syntax <type>... <varargname>
- Example:
public class VarArgs {
public static void main(String[] args) {
System.out.println(sum(2, 3, 4));
}
public static int sum(int... nums) {
int sum = 0;
for(int i : nums) {
sum += i;
}
return sum;
}
}
- The ellipsis can be located anywhere e.g. (int... nums) or (int ...nums) or (int ... nums) is fine.
- Essentially the method arguments are implicitly converted into an array and passed to the method. so nums is an int[] array.
- Example main() can be legally rewritten as :
public static void main(String... args) {
}
- For a var-args method, the method parameters can also be passed as an array argument.
- Example:
public class VarArgs {
public static void main(String[] args) {
System.out.println(vasum(2, 3, 4)); //Variable arguments invocation
System.out.println(vasum(new int[] {1, 2, 3}); //Array invocation also OK for var-args
System.out.println(arrsum(new int[] {2, 3, 4})); //Only Array invocation is possible
}
public static int vasum(int ... nums) {
int sum = 0;
for(int i : nums) {
sum += i;
}
return sum;
}
public static int arrsum(int[] nums) {
int sum = 0;
for(int i : nums) {
sum += i;
}
return sum;
}
}
- The var-args must be the last parameter in the method's signature. Why ? To resolve situations like this :
sum2(2, 3);
public static void sum2(int a, int... nums) {
}
- Only one var-arg can be declared in the method (even if the var-args are of different types)
public static void sum3( String... strs, int... nums) { //ILLEGAL
}