How to append into first element of Arraylist?

For eg:- my Arraylist is :-
[S1 10 20 12, S2 11 21 13, S3 13 10 12]
Thus i want to add extra element (99) in first place keeping previous ones as they were [S1 10 20 12]
My output should be [S1 10 20 12 99, S2 11 21 13, S3 13 10 12]

Use the get method to read the first element from the list, and the set method to write the modified value. Read the API documentation to see what methods are available for lists: https://docs.oracle.com/javase/10/docs/api/java/util/List.html

String firstItem = list.get(0);
list.set(0, firstItem + " 99");

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# 答案2
**得分**: 1

Use add with index as first parameter: 使用带有索引作为第一个参数的add方法：public void add(int index, E element)

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<summary>英文:</summary>

Use add with index as first parameter: public void add(int index, E element)

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# 答案3
**得分**: 0

你可以考虑使用链表（LinkedList），如果这个列表非常大，插入操作会更加便宜。

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<summary>英文:</summary>

You might want to consider a LinkedList where insertion is cheaper if this list is very big.

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# 答案4
**得分**: 0

你可以使用```LinkedList.addFirst()```，它具有最佳性能。但你必须记住，你需要将你的列表声明为```LinkedList```实例，而不是更通用的接口```List```。

第二种方法是使用两个参数的```List.add(int index, E Element)```方法。然后你可以将你的列表声明为```List```。

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<summary>英文:</summary>

You can use ```LinkedList.addFirst()``` which has the best performance. But you have to remember, that you are obligated to declare instance your list as ```LinkedList```, instead of a more universal interface ```List```.

The second way is to use two arguments ```List.add(int index, E Element)``` method. Then you can have your list declared as ```List```.

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