I want to make a list with kotlin and java!

Introduction ...

This article was written in 2 previous articles,

** 3rd day of article posting every day for 7 days **

It has become

The code to use is pasted below, but see the article two years before for the detailed features of this app!

--java version: https://github.com/sato-na/guruwake_java

--kotlin version: https://github.com/sato-na/guruwake_kotlin

↓ This is the main subject of this article ↓

To work with lists in each language ...

-- table of contents --

1. How to make an Arraylist

2. How to add / remove elements

3. How to get the number of elements

4. How to reverse / shuffle the contents of the list

5. How to copy the contents to a different list

How to make an ArrayList

--For java

ArrayList<Element type>Variable name= new ArrayList<>();

Example)

WhoActivity.java

ArrayList<String>memberL = new ArrayList<>();  //20th line

Very different from variable definition

--For kotlin

val/var variable name:ArrayList<Element type> = arrayListOf()

Example)

WhoActivity.kt

var memberL:ArrayList<String> = arrayListOf()  //13th line

Similar to variable definition except how to specify the contents of the list

The method of specifying the element type is very similar for both

How to add / remove elements

--For java

//add to
List name.add(element);
//Delete
List name.remove(Element location);

Example)

WhoActivity.java

//add to
memberL.add(memberET.getText().toString());  //Line 82

• .GetText () will be explained at a later date.

ResultActivity.java

//Delete
memberL.remove(0);  //Line 46

--For kotlin

//add to
List name.add(element)
//Delete
List name.remove(element)

Example)

WhoActivity.kt

//add to
memberL.add(member_et.text.toString())  //Line 54

• .Text will be explained at a later date.

ResultActivity.kt

//Delete
memberL.remove(memberL[0])  //Line 37

The method of adding is the same, but when deleting, the one used to specify the target element is different.

How to get the number of elements

--For java

List name.size();

Example)

resultActivity.java

int memberNum = memberL.size();  //Line 33

--For kotlin

List name.size

Example)

ResultActivity.kt

val memberNum = memberL.size  //24th line

java is very similar to .size () and kotlin is very similar to .size

How to reverse / shuffle the contents of the list

--For java

//Reverse order
Collections.reverse(List name);
//shuffle
Collections.shuffle(List name);

Example)

WhoActivity.java

//Reverse order
ArrayList<String> memberLR = (ArrayList<String>) memberL.clone();  //Line 84
Collections.reverse(memberLR);

• Refer to "How to copy the contents to a different list" for the processing contents of the first line.

resultActivity.java

//shuffle
Collections.shuffle(memberL);  //Line 34

--For kotlin

//Reverse order
List name.reverse()
//shuffle
List name.shuffle(Random())

Example)

WhoActivity.kt

//Reverse order
var memverLR = ArrayList<String>(memberL)  //Line 56
memverLR.reverse()

• Refer to "How to copy the contents to a different list" for the processing contents of the first line.

ResultActivity.kt

//shuffle
memberL.shuffle(Random())  //25th line

The writing style is very different, but both The keywords are "reverse" for reverse order and "shuffle" for shuffle.

How to copy the contents to a different list

--For java

ArrayList<Element type>Variable name= (ArrayList<Element type>)List name to copy.clone();

Example)

WhoActivity.java

ArrayList<String> memberLR = (ArrayList<String>) memberL.clone();  //Line 84

--For kotlin

val/var variable name= ArrayList<Element type>(List name to copy)

Example)

WhoActivity.kt

var memverLR = ArrayList<String>(memberL)  //Line 56

java uses .clone (), kotlin is a little different from the list definition method

Finally…

This time I defined the list in java and kotlin. I think there are still many features, so I hope I can write an article when it comes out in other code.

In addition, the schedule from today has been slightly changed from the schedule described on the first day. I'll change the schedule of that article, so it doesn't really matter. I will write it here for my own memo.

I will post an article tomorrow, so please keep an eye on me.