How replace one list items with another in java?

Question

I have two array lists, Can it possible to replace the one list items with the second list.

ArrayList<String> a = new ArrayList<String>();
ArrayList<String> b = new ArrayList<String>();
a.add("testone");
a.add("testtwo");
a.add("testthree");
b.add("demoone");
b.add("demotwo");
System.out.println("List values are: "+ a);

Is there any way to replace the first list with the second list elements. So if I print first array list, it should print the following output

[demoone, demotwo] 

Answer 1

最简单的方法是将列表b分配给列表a

a=b

Answer 2

I guess you need:

a = b;
System.out.println("List values are: "+ a);

Answer 3

Option 1:

a = b; //copy same list reference

Option 2:

a.clear(); //clear all existing items
a.addAll(b); //copy all

Option 3:

a = (ArrayList<String>)b.clone(); //shallow copy

Answer 4

So there are two ways to do this based on requirement.

1. You need the list referenced by reference variable b to be available with the reference variable a . In this case the original list referenced by a is not required to be modified, just the reference variable a is being pointed to the second list (originally referenced by reference variable b ).

    a = b; System.out.println("List values are: "+ a); 

2. You need the list referenced by reference variable a to have the items present in the list referenced by b . In this case, the actual list originally referenced by a has to be modified. This might be required when you are passing the list to a method which is supposed to modify the list.

    a.clear(); a.addAll(b); System.out.println("List values are: "+ a);