Java convert ArrayList to string and back to ArrayList?

I wanted to save an ArrayList to SharedPreferences so I need to turn it into a string and back, this is what I am doing:

// Save to shared preferences

SharedPreferences sharedPref = this.getPreferences(Activity.MODE_PRIVATE);

SharedPreferences.Editor editor = this.getPreferences(Activity.MODE_PRIVATE).edit();

editor.putString("myAppsArr", myAppsArr.toString());

editor.commit();

I can retrieve it with String arrayString = sharedPref.getString("yourKey", null); but I don't know how to convert arrayString back into an ArrayList. How can it be done?

My array looks something like:

[item1,item2,item3]

edited Jan 15 '13 at 10:54

Eng.Fouad

84.8k53247360

asked Sep 5 '12 at 7:07

lisovaccaro

6,87777212357

add a comment |

I wanted to save an ArrayList to SharedPreferences so I need to turn it into a string and back, this is what I am doing:

// Save to shared preferences

SharedPreferences sharedPref = this.getPreferences(Activity.MODE_PRIVATE);

SharedPreferences.Editor editor = this.getPreferences(Activity.MODE_PRIVATE).edit();

editor.putString("myAppsArr", myAppsArr.toString());

editor.commit();

I can retrieve it with String arrayString = sharedPref.getString("yourKey", null); but I don't know how to convert arrayString back into an ArrayList. How can it be done?

My array looks something like:

[item1,item2,item3]

edited Jan 15 '13 at 10:54

Eng.Fouad

84.8k53247360

asked Sep 5 '12 at 7:07

lisovaccaro

6,87777212357

add a comment |

I wanted to save an ArrayList to SharedPreferences so I need to turn it into a string and back, this is what I am doing:

// Save to shared preferences

SharedPreferences sharedPref = this.getPreferences(Activity.MODE_PRIVATE);

SharedPreferences.Editor editor = this.getPreferences(Activity.MODE_PRIVATE).edit();

editor.putString("myAppsArr", myAppsArr.toString());

editor.commit();

I can retrieve it with String arrayString = sharedPref.getString("yourKey", null); but I don't know how to convert arrayString back into an ArrayList. How can it be done?

My array looks something like:

[item1,item2,item3]

edited Jan 15 '13 at 10:54

Eng.Fouad

84.8k53247360

asked Sep 5 '12 at 7:07

lisovaccaro

6,87777212357

I wanted to save an ArrayList to SharedPreferences so I need to turn it into a string and back, this is what I am doing:

// Save to shared preferences

SharedPreferences sharedPref = this.getPreferences(Activity.MODE_PRIVATE);

SharedPreferences.Editor editor = this.getPreferences(Activity.MODE_PRIVATE).edit();

editor.putString("myAppsArr", myAppsArr.toString());

editor.commit();

I can retrieve it with String arrayString = sharedPref.getString("yourKey", null); but I don't know how to convert arrayString back into an ArrayList. How can it be done?

My array looks something like:

[item1,item2,item3]

java android string list arraylist

edited Jan 15 '13 at 10:54

Eng.Fouad

84.8k53247360

asked Sep 5 '12 at 7:07

lisovaccaro

6,87777212357

edited Jan 15 '13 at 10:54

Eng.Fouad

84.8k53247360

asked Sep 5 '12 at 7:07

lisovaccaro

6,87777212357

edited Jan 15 '13 at 10:54

Eng.Fouad

84.8k53247360

edited Jan 15 '13 at 10:54

Eng.Fouad

84.8k53247360

edited Jan 15 '13 at 10:54

Eng.Fouad

84.8k53247360

asked Sep 5 '12 at 7:07

lisovaccaro

6,87777212357

asked Sep 5 '12 at 7:07

lisovaccaro

6,87777212357

asked Sep 5 '12 at 7:07

lisovaccaro

6,87777212357

add a comment |

6 Answers
6

active

oldest

votes

+50

You have 2 choices :

Manually parse the string and recreate the arraylist. This would be pretty tedious.

Use a JSON library like Google's Gson library to store and retrieve objects as JSON strings. This is a lightweight library, well regarded and popular. It would be an ideal solution in your case with minimal work required. e.g.,

// How to store JSON string

Gson gson = new Gson();

// This can be any object. Does not have to be an arraylist.

String json = gson.toJson(myAppsArr);



// How to retrieve your Java object back from the string

Gson gson = new Gson();

DataObject obj = gson.fromJson(arrayString, ArrayList.class);

edited Jan 13 '13 at 23:57

answered Jan 13 '13 at 23:48

Dhruv Gairola

7,71833238

I changed the array elements to strings, I'm sure it must be a lot easier now.

– lisovaccaro
Jan 13 '13 at 23:51

It doesn't matter. With Gson, you can convert any java object to a string and then convert it back. So even if you have an arraylist of custom objects, there's no problem.

– Dhruv Gairola
Jan 13 '13 at 23:54

add a comment |

Try this

ArrayList<String> array = Arrays.asList(arrayString.split(","))

This will work if comma is used as separator and none of the items have it.

answered Jan 14 '13 at 0:19

Mykhailo Gaidai

2,73011322

add a comment |

I ended up using:

ArrayList<String> appList = new ArrayList<String>(Arrays.asList(appsString.split("\s*,\s*")));

This doesn't work for all array types though. This option differs from:

ArrayList<String> array = Arrays.asList(arrayString.split(","));

on that the second option creates an inmutable array.

answered Jan 15 '13 at 21:55

lisovaccaro

6,87777212357

Did you see my answer?

– Eng.Fouad
Jan 16 '13 at 3:32

add a comment |

The page http://mjiayou.com/2015/07/22/exception-gson-internal-cannot-be-cast-to/ contains the following:

Type     type  = new TypeToken<List<T>>(){}.getType();

List<T>  list  = gson.fromJson(jsonString, type)

perhaps it will be helpful.

edited Jan 6 '16 at 17:14

John Hascall

7,56643560

answered Jan 6 '16 at 13:29

user5752479

111

add a comment |

      //arraylist convert into String using Gson 

      Gson gson = new Gson();

      String data = gson.toJson(myArrayList);

      Log.e(TAG, "json:" + gson);



      //String to ArrayList



      Gson gson = new Gson();

      arrayList=gson.fromJson(data, new TypeToken<List<Friends>>()

      {}.getType());

edited Jan 9 at 6:57

answered Jun 11 '18 at 10:21

bhoomika

43159

add a comment |

Update to Dhruv Gairola's answer for Kotlin

val gson = Gson();

val jsonString = gson.toJson(arrayList)

answered Oct 9 '18 at 8:00

Quick learner

2,4861924

add a comment |

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6 Answers
6

active

oldest

votes

6 Answers
6

active

oldest

votes

+50

You have 2 choices :

Manually parse the string and recreate the arraylist. This would be pretty tedious.

// How to store JSON string

Gson gson = new Gson();

// This can be any object. Does not have to be an arraylist.

String json = gson.toJson(myAppsArr);



// How to retrieve your Java object back from the string

Gson gson = new Gson();

DataObject obj = gson.fromJson(arrayString, ArrayList.class);

edited Jan 13 '13 at 23:57

answered Jan 13 '13 at 23:48

Dhruv Gairola

7,71833238

I changed the array elements to strings, I'm sure it must be a lot easier now.

– lisovaccaro
Jan 13 '13 at 23:51

It doesn't matter. With Gson, you can convert any java object to a string and then convert it back. So even if you have an arraylist of custom objects, there's no problem.

– Dhruv Gairola
Jan 13 '13 at 23:54

add a comment |

+50

You have 2 choices :

Manually parse the string and recreate the arraylist. This would be pretty tedious.

// How to store JSON string

Gson gson = new Gson();

// This can be any object. Does not have to be an arraylist.

String json = gson.toJson(myAppsArr);



// How to retrieve your Java object back from the string

Gson gson = new Gson();

DataObject obj = gson.fromJson(arrayString, ArrayList.class);

edited Jan 13 '13 at 23:57

answered Jan 13 '13 at 23:48

Dhruv Gairola

7,71833238

I changed the array elements to strings, I'm sure it must be a lot easier now.

– lisovaccaro
Jan 13 '13 at 23:51

It doesn't matter. With Gson, you can convert any java object to a string and then convert it back. So even if you have an arraylist of custom objects, there's no problem.

– Dhruv Gairola
Jan 13 '13 at 23:54

add a comment |

+50

You have 2 choices :

Manually parse the string and recreate the arraylist. This would be pretty tedious.

// How to store JSON string

Gson gson = new Gson();

// This can be any object. Does not have to be an arraylist.

String json = gson.toJson(myAppsArr);



// How to retrieve your Java object back from the string

Gson gson = new Gson();

DataObject obj = gson.fromJson(arrayString, ArrayList.class);

edited Jan 13 '13 at 23:57

answered Jan 13 '13 at 23:48

Dhruv Gairola

7,71833238

You have 2 choices :

Manually parse the string and recreate the arraylist. This would be pretty tedious.

// How to store JSON string

Gson gson = new Gson();

// This can be any object. Does not have to be an arraylist.

String json = gson.toJson(myAppsArr);



// How to retrieve your Java object back from the string

Gson gson = new Gson();

DataObject obj = gson.fromJson(arrayString, ArrayList.class);

edited Jan 13 '13 at 23:57

answered Jan 13 '13 at 23:48

Dhruv Gairola

7,71833238

edited Jan 13 '13 at 23:57

answered Jan 13 '13 at 23:48

Dhruv Gairola

7,71833238

answered Jan 13 '13 at 23:48

Dhruv Gairola

7,71833238

answered Jan 13 '13 at 23:48

Dhruv Gairola

7,71833238

I changed the array elements to strings, I'm sure it must be a lot easier now.

– lisovaccaro
Jan 13 '13 at 23:51

It doesn't matter. With Gson, you can convert any java object to a string and then convert it back. So even if you have an arraylist of custom objects, there's no problem.

– Dhruv Gairola
Jan 13 '13 at 23:54

add a comment |

I changed the array elements to strings, I'm sure it must be a lot easier now.

– lisovaccaro
Jan 13 '13 at 23:51

It doesn't matter. With Gson, you can convert any java object to a string and then convert it back. So even if you have an arraylist of custom objects, there's no problem.

– Dhruv Gairola
Jan 13 '13 at 23:54

I changed the array elements to strings, I'm sure it must be a lot easier now.

– lisovaccaro
Jan 13 '13 at 23:51

It doesn't matter. With Gson, you can convert any java object to a string and then convert it back. So even if you have an arraylist of custom objects, there's no problem.

– Dhruv Gairola
Jan 13 '13 at 23:54

add a comment |

Try this

ArrayList<String> array = Arrays.asList(arrayString.split(","))

This will work if comma is used as separator and none of the items have it.

answered Jan 14 '13 at 0:19

Mykhailo Gaidai

2,73011322

add a comment |

Try this

ArrayList<String> array = Arrays.asList(arrayString.split(","))

This will work if comma is used as separator and none of the items have it.

answered Jan 14 '13 at 0:19

Mykhailo Gaidai

2,73011322

add a comment |

Try this

ArrayList<String> array = Arrays.asList(arrayString.split(","))

This will work if comma is used as separator and none of the items have it.

answered Jan 14 '13 at 0:19

Mykhailo Gaidai

2,73011322

Try this

ArrayList<String> array = Arrays.asList(arrayString.split(","))

This will work if comma is used as separator and none of the items have it.

answered Jan 14 '13 at 0:19

Mykhailo Gaidai

2,73011322

answered Jan 14 '13 at 0:19

Mykhailo Gaidai

2,73011322

answered Jan 14 '13 at 0:19

Mykhailo Gaidai

2,73011322

answered Jan 14 '13 at 0:19

Mykhailo Gaidai

2,73011322

add a comment |

I ended up using:

ArrayList<String> appList = new ArrayList<String>(Arrays.asList(appsString.split("\s*,\s*")));

This doesn't work for all array types though. This option differs from:

ArrayList<String> array = Arrays.asList(arrayString.split(","));

on that the second option creates an inmutable array.

answered Jan 15 '13 at 21:55

lisovaccaro

6,87777212357

Did you see my answer?

– Eng.Fouad
Jan 16 '13 at 3:32

add a comment |

I ended up using:

ArrayList<String> appList = new ArrayList<String>(Arrays.asList(appsString.split("\s*,\s*")));

This doesn't work for all array types though. This option differs from:

ArrayList<String> array = Arrays.asList(arrayString.split(","));

on that the second option creates an inmutable array.

answered Jan 15 '13 at 21:55

lisovaccaro

6,87777212357

Did you see my answer?

– Eng.Fouad
Jan 16 '13 at 3:32

add a comment |

I ended up using:

ArrayList<String> appList = new ArrayList<String>(Arrays.asList(appsString.split("\s*,\s*")));

This doesn't work for all array types though. This option differs from:

ArrayList<String> array = Arrays.asList(arrayString.split(","));

on that the second option creates an inmutable array.

answered Jan 15 '13 at 21:55

lisovaccaro

6,87777212357

I ended up using:

ArrayList<String> appList = new ArrayList<String>(Arrays.asList(appsString.split("\s*,\s*")));

This doesn't work for all array types though. This option differs from:

ArrayList<String> array = Arrays.asList(arrayString.split(","));

on that the second option creates an inmutable array.

answered Jan 15 '13 at 21:55

lisovaccaro

6,87777212357

answered Jan 15 '13 at 21:55

lisovaccaro

6,87777212357

answered Jan 15 '13 at 21:55

lisovaccaro

6,87777212357

answered Jan 15 '13 at 21:55

lisovaccaro

6,87777212357

Did you see my answer?

– Eng.Fouad
Jan 16 '13 at 3:32

add a comment |

Did you see my answer?

– Eng.Fouad
Jan 16 '13 at 3:32

Did you see my answer?

– Eng.Fouad
Jan 16 '13 at 3:32

add a comment |

The page http://mjiayou.com/2015/07/22/exception-gson-internal-cannot-be-cast-to/ contains the following:

Type     type  = new TypeToken<List<T>>(){}.getType();

List<T>  list  = gson.fromJson(jsonString, type)

perhaps it will be helpful.

edited Jan 6 '16 at 17:14

John Hascall

7,56643560

answered Jan 6 '16 at 13:29

user5752479

111

add a comment |

The page http://mjiayou.com/2015/07/22/exception-gson-internal-cannot-be-cast-to/ contains the following:

Type     type  = new TypeToken<List<T>>(){}.getType();

List<T>  list  = gson.fromJson(jsonString, type)

perhaps it will be helpful.

edited Jan 6 '16 at 17:14

John Hascall

7,56643560

answered Jan 6 '16 at 13:29

user5752479

111

add a comment |

The page http://mjiayou.com/2015/07/22/exception-gson-internal-cannot-be-cast-to/ contains the following:

Type     type  = new TypeToken<List<T>>(){}.getType();

List<T>  list  = gson.fromJson(jsonString, type)

perhaps it will be helpful.

edited Jan 6 '16 at 17:14

John Hascall

7,56643560

answered Jan 6 '16 at 13:29

user5752479

111

The page http://mjiayou.com/2015/07/22/exception-gson-internal-cannot-be-cast-to/ contains the following:

Type     type  = new TypeToken<List<T>>(){}.getType();

List<T>  list  = gson.fromJson(jsonString, type)

perhaps it will be helpful.

edited Jan 6 '16 at 17:14

John Hascall

7,56643560

answered Jan 6 '16 at 13:29

user5752479

111

edited Jan 6 '16 at 17:14

John Hascall

7,56643560

edited Jan 6 '16 at 17:14

John Hascall

7,56643560

edited Jan 6 '16 at 17:14

John Hascall

7,56643560

answered Jan 6 '16 at 13:29

user5752479

111

answered Jan 6 '16 at 13:29

user5752479

111

answered Jan 6 '16 at 13:29

user5752479

111

add a comment |

      //arraylist convert into String using Gson 

      Gson gson = new Gson();

      String data = gson.toJson(myArrayList);

      Log.e(TAG, "json:" + gson);



      //String to ArrayList



      Gson gson = new Gson();

      arrayList=gson.fromJson(data, new TypeToken<List<Friends>>()

      {}.getType());

edited Jan 9 at 6:57

answered Jun 11 '18 at 10:21

bhoomika

43159

add a comment |

      //arraylist convert into String using Gson 

      Gson gson = new Gson();

      String data = gson.toJson(myArrayList);

      Log.e(TAG, "json:" + gson);



      //String to ArrayList



      Gson gson = new Gson();

      arrayList=gson.fromJson(data, new TypeToken<List<Friends>>()

      {}.getType());

edited Jan 9 at 6:57

answered Jun 11 '18 at 10:21

bhoomika

43159

add a comment |

      //arraylist convert into String using Gson 

      Gson gson = new Gson();

      String data = gson.toJson(myArrayList);

      Log.e(TAG, "json:" + gson);



      //String to ArrayList



      Gson gson = new Gson();

      arrayList=gson.fromJson(data, new TypeToken<List<Friends>>()

      {}.getType());

edited Jan 9 at 6:57

answered Jun 11 '18 at 10:21

bhoomika

43159

      //arraylist convert into String using Gson 

      Gson gson = new Gson();

      String data = gson.toJson(myArrayList);

      Log.e(TAG, "json:" + gson);



      //String to ArrayList



      Gson gson = new Gson();

      arrayList=gson.fromJson(data, new TypeToken<List<Friends>>()

      {}.getType());

edited Jan 9 at 6:57

answered Jun 11 '18 at 10:21

bhoomika

43159

edited Jan 9 at 6:57

answered Jun 11 '18 at 10:21

bhoomika

43159

answered Jun 11 '18 at 10:21

bhoomika

43159

answered Jun 11 '18 at 10:21

bhoomika

43159

add a comment |

Update to Dhruv Gairola's answer for Kotlin

val gson = Gson();

val jsonString = gson.toJson(arrayList)

answered Oct 9 '18 at 8:00

Quick learner

2,4861924

add a comment |

Update to Dhruv Gairola's answer for Kotlin

val gson = Gson();

val jsonString = gson.toJson(arrayList)

answered Oct 9 '18 at 8:00

Quick learner

2,4861924

add a comment |

Update to Dhruv Gairola's answer for Kotlin

val gson = Gson();

val jsonString = gson.toJson(arrayList)

answered Oct 9 '18 at 8:00

Quick learner

2,4861924

Update to Dhruv Gairola's answer for Kotlin

val gson = Gson();

val jsonString = gson.toJson(arrayList)

answered Oct 9 '18 at 8:00

Quick learner

2,4861924

answered Oct 9 '18 at 8:00

Quick learner

2,4861924

answered Oct 9 '18 at 8:00

Quick learner

2,4861924

answered Oct 9 '18 at 8:00

Quick learner

2,4861924

add a comment |

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