Javaの差分リスト

２つのArrayList、Setなどの差分を取りたい際の自分用の備忘録。

(ArrayList, Set) a1, a2;
a1.removeAll(a2)
a2.removeAll(a1)
の形でa1-a2, a2-a1の差分リストを取得可能。a1, a2はCollection型であれば型が一致している必要はない。

以下実験コードと結果。

コード:

ArrayList<String> arr1 = new ArrayList<String>() {
    private static final long serialVersionUID = 1L;
    {
        add("a");
        add("b");
        add("c");
        add("d");
        add("e");
    }
};

ArrayList<String> arr2 = new ArrayList<String>(arr1);
arr2.remove(0);
arr2.remove(0);
arr2.add("f");

System.out.println("arr1");
for (String s : arr1) {
    System.out.println(s);
}
System.out.println("--------");

System.out.println("arr2");
for (String s : arr2) {
    System.out.println(s);
}
System.out.println("--------");

System.out.println();

ArrayList<String> subArr1 = new ArrayList<String>(arr1);
subArr1.removeAll(arr2);
System.out.println("subArr1");
for (String s : subArr1) {
    System.out.println(s);
}
System.out.println("-------");

ArrayList<String> subArr2 = new ArrayList<String>(arr2);
subArr2.removeAll(arr1);
System.out.println("subArr2");
for (String s: subArr2) {
    System.out.println(s);
}
System.out.println("-------");

System.out.println();

Set<String> set1 = new HashSet<String>();
set1.add("a");
set1.add("b");
set1.add("c");
set1.add("d");
set1.add("e");

Set<String> set2 = new HashSet<String>(set1);
set2.remove("a");
set2.remove("b");
set2.add("f");

System.out.println("set1");
for (String s : set1) {
    System.out.println(s);
}
System.out.println("--------");

System.out.println("set2");
for (String s : set2) {
    System.out.println(s);
}
System.out.println("-------");

System.out.println();

Set<String> subSet1 = new HashSet<String>(set1);
subSet1.removeAll(set2);
System.out.println("subSet1");
for (String s : subSet1) {
    System.out.println(s);
}
System.out.println("-------");

Set<String> subSet2 = new HashSet<String>(set2);
System.out.println("subSet2");
subSet2.removeAll(set1);
for (String s: subSet2) {
    System.out.println(s);
}
System.out.println("-------");

System.out.println();

ArrayList<String> subArrWithSet = new ArrayList<String>(set1);
subArrWithSet.removeAll(arr2);
System.out.println("subArrWithSet");
for (String s : subArrWithSet) {
    System.out.println(s);
}
System.out.println("-------");

結果 :

arr1
a
b
c
d
e
--------
arr2
c
d
e
f
--------

subArr1
a
b
-------
subArr2
f
-------

set1
a
b
c
d
e
--------
set2
c
d
e
f
-------

subSet1
a
b
-------
subSet2
f
-------

subArrWithSet
a
b
-------