Difference between ArrayList iList = new ArrayList(); and ArrayList iList = new ArrayList(); [duplicate]

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This question already has an answer here:

ArrayList Generic without Type

5 answers

What is the difference between this two line:

ArrayList<Integer> iList = new ArrayList<Integer>();

ArrayList iList = new ArrayList<Integer>();

Step 1: raise a compile time error

public static void main(String args){

    ArrayList<Integer> iList = new ArrayList<Integer>();

    iList.add(10);

    iList.add("Test_Element"); // Compiler error, while trying to insert a String in an Integer ArrayList 

    System.out.print("Value of 2nd element: " + iList.get(1));

 }

Step 2: works fine

public static void main(String args){

    ArrayList iList = new ArrayList<Integer>();

    iList.add(10);

    iList.add("Test_Element"); // works fine, while trying to insert a String in an Integer ArrayList 

    System.out.print("Value of 2nd element: " + iList.get(1));

 }

Output:
Value of 2nd element: Test_Element

I am expecting an error like

"add(java.lang.Integer) in ArrayList cannot be applied to (java.lang.String)", but in step2 two it works fine.

Could anyone please explain me, why I am able to insert a String in this list.

edited Jan 3 at 7:25

asked Jan 3 at 7:10

SKG

192

marked as duplicate by Denys Séguret java
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Jan 3 at 7:16

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1

check out stackoverflow.com/questions/25689673/…

– johnheroy
Jan 3 at 7:14

2

That is because of raw types. Don't use them.

– MC Emperor
Jan 3 at 7:17

You will not get any error, because your second type is Generic. You can add any type of object inside your second ArrayList

– Vishwajit R. Shinde
Jan 3 at 7:29

add a comment |

This question already has an answer here:

ArrayList Generic without Type

5 answers

What is the difference between this two line:

ArrayList<Integer> iList = new ArrayList<Integer>();

ArrayList iList = new ArrayList<Integer>();

Step 1: raise a compile time error

public static void main(String args){

    ArrayList<Integer> iList = new ArrayList<Integer>();

    iList.add(10);

    iList.add("Test_Element"); // Compiler error, while trying to insert a String in an Integer ArrayList 

    System.out.print("Value of 2nd element: " + iList.get(1));

 }

Step 2: works fine

public static void main(String args){

    ArrayList iList = new ArrayList<Integer>();

    iList.add(10);

    iList.add("Test_Element"); // works fine, while trying to insert a String in an Integer ArrayList 

    System.out.print("Value of 2nd element: " + iList.get(1));

 }

Output:
Value of 2nd element: Test_Element

I am expecting an error like

"add(java.lang.Integer) in ArrayList cannot be applied to (java.lang.String)", but in step2 two it works fine.

Could anyone please explain me, why I am able to insert a String in this list.

edited Jan 3 at 7:25

asked Jan 3 at 7:10

SKG

192

marked as duplicate by Denys Séguret java
Users with the java badge can single-handedly close java questions as duplicates and reopen them as needed.

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Jan 3 at 7:16

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1

check out stackoverflow.com/questions/25689673/…

– johnheroy
Jan 3 at 7:14

2

That is because of raw types. Don't use them.

– MC Emperor
Jan 3 at 7:17

You will not get any error, because your second type is Generic. You can add any type of object inside your second ArrayList

– Vishwajit R. Shinde
Jan 3 at 7:29

add a comment |

This question already has an answer here:

ArrayList Generic without Type

5 answers

What is the difference between this two line:

ArrayList<Integer> iList = new ArrayList<Integer>();

ArrayList iList = new ArrayList<Integer>();

Step 1: raise a compile time error

public static void main(String args){

    ArrayList<Integer> iList = new ArrayList<Integer>();

    iList.add(10);

    iList.add("Test_Element"); // Compiler error, while trying to insert a String in an Integer ArrayList 

    System.out.print("Value of 2nd element: " + iList.get(1));

 }

Step 2: works fine

public static void main(String args){

    ArrayList iList = new ArrayList<Integer>();

    iList.add(10);

    iList.add("Test_Element"); // works fine, while trying to insert a String in an Integer ArrayList 

    System.out.print("Value of 2nd element: " + iList.get(1));

 }

Output:
Value of 2nd element: Test_Element

I am expecting an error like

"add(java.lang.Integer) in ArrayList cannot be applied to (java.lang.String)", but in step2 two it works fine.

Could anyone please explain me, why I am able to insert a String in this list.

edited Jan 3 at 7:25

asked Jan 3 at 7:10

SKG

192

This question already has an answer here:

ArrayList Generic without Type

5 answers

What is the difference between this two line:

ArrayList<Integer> iList = new ArrayList<Integer>();

ArrayList iList = new ArrayList<Integer>();

Step 1: raise a compile time error

public static void main(String args){

    ArrayList<Integer> iList = new ArrayList<Integer>();

    iList.add(10);

    iList.add("Test_Element"); // Compiler error, while trying to insert a String in an Integer ArrayList 

    System.out.print("Value of 2nd element: " + iList.get(1));

 }

Step 2: works fine

public static void main(String args){

    ArrayList iList = new ArrayList<Integer>();

    iList.add(10);

    iList.add("Test_Element"); // works fine, while trying to insert a String in an Integer ArrayList 

    System.out.print("Value of 2nd element: " + iList.get(1));

 }

Output:
Value of 2nd element: Test_Element

I am expecting an error like

"add(java.lang.Integer) in ArrayList cannot be applied to (java.lang.String)", but in step2 two it works fine.

Could anyone please explain me, why I am able to insert a String in this list.

This question already has an answer here:

ArrayList Generic without Type

5 answers

java generics arraylist

edited Jan 3 at 7:25

asked Jan 3 at 7:10

SKG

192

edited Jan 3 at 7:25

asked Jan 3 at 7:10

SKG

192

edited Jan 3 at 7:25

asked Jan 3 at 7:10

SKG

192

asked Jan 3 at 7:10

SKG

192

asked Jan 3 at 7:10

SKG

192

marked as duplicate by Denys Séguret java
Users with the java badge can single-handedly close java questions as duplicates and reopen them as needed.

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Jan 3 at 7:16

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

marked as duplicate by Denys Séguret java
Users with the java badge can single-handedly close java questions as duplicates and reopen them as needed.

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Jan 3 at 7:16

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1

check out stackoverflow.com/questions/25689673/…

– johnheroy
Jan 3 at 7:14

2

That is because of raw types. Don't use them.

– MC Emperor
Jan 3 at 7:17

You will not get any error, because your second type is Generic. You can add any type of object inside your second ArrayList

– Vishwajit R. Shinde
Jan 3 at 7:29

add a comment |

1

check out stackoverflow.com/questions/25689673/…

– johnheroy
Jan 3 at 7:14

2

That is because of raw types. Don't use them.

– MC Emperor
Jan 3 at 7:17

You will not get any error, because your second type is Generic. You can add any type of object inside your second ArrayList

– Vishwajit R. Shinde
Jan 3 at 7:29

check out stackoverflow.com/questions/25689673/…

– johnheroy
Jan 3 at 7:14

That is because of raw types. Don't use them.

– MC Emperor
Jan 3 at 7:17

You will not get any error, because your second type is Generic. You can add any type of object inside your second ArrayList

– Vishwajit R. Shinde
Jan 3 at 7:29

add a comment |

1 Answer
1

active

oldest

votes

There's no compile-time check on generic type of ArrayList when you write ArrayList list = new ArrayList<Integer>(). The generic type on the right side of the assignment expression is basically ignored. ArrayList doesn't really have an inner type, just that the T in ArrayList<T> helps you make sure you only perform operations with instances of T on your list.

It would be useful to understand why you want to have integers and strings mixed in the same ArrayList--there might be a design smell here :)

answered Jan 3 at 7:16

johnheroy

32616

add a comment |

1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

It would be useful to understand why you want to have integers and strings mixed in the same ArrayList--there might be a design smell here :)

answered Jan 3 at 7:16

johnheroy

32616

add a comment |

It would be useful to understand why you want to have integers and strings mixed in the same ArrayList--there might be a design smell here :)

answered Jan 3 at 7:16

johnheroy

32616

add a comment |

It would be useful to understand why you want to have integers and strings mixed in the same ArrayList--there might be a design smell here :)

answered Jan 3 at 7:16

johnheroy

32616

It would be useful to understand why you want to have integers and strings mixed in the same ArrayList--there might be a design smell here :)

answered Jan 3 at 7:16

johnheroy

32616

answered Jan 3 at 7:16

johnheroy

32616

answered Jan 3 at 7:16

johnheroy

32616

answered Jan 3 at 7:16

johnheroy

32616

add a comment |

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