Find all the paths of tree that add to a input value
public AllPathsAddingSum(List&lt;Integer&gt; items) { 
    create (items);
};


Unneeded space, unneeded semicolon. Consider autoformatting your code.

for (Integer i : path) {
    System.out.print(i + " ");
}
System.out.println();


This section in computePaths is doing something different than the function description. It doesn't calculate, it prints.

Move it to a separate method. Then give the class a PrintStream to use. This PrintStream would be System.out, or a dummy PrintStream that just copies everything to an internal buffer.

Then you can unittest your code.