Java solution without for loop
\npublic int[] getConcatenation(int[] nums) {\n        int[] ans = new int[nums.length<<1];\n        System.arraycopy(nums, 0, ans, 0, nums.length);\n        Sy
```    \npublic int[] getConcatenation(int[] nums) {\n        int[] ans = new int[nums.length<<1];\n        System.arraycopy(nums, 0, ans, 0, nums.length);\n        System.arraycopy(nums, 0, ans, nums.length, nums.length);\n        return ans;\n}\n```\n\n```\n1. System.arraycopy(..) is a native method call in JVM and will be faster than using a for loop.\n2. nums.length<<1  instead of nums.length*2 is preferred for faster operations.\n```\n
['Java']