Guava immutable set

Creating an immutable copy of an object is always a good defensive skill .

Guava For all the JDK Standard set types and Guava New collection types are available in an easy-to-use, immutable version

Advantages of immutable objects

• When an object is called by an untrusted library , Immutable forms are safe

• When an immutable object is called by multiple threads , No race condition problem

• Immutable sets do not need to consider changes , So it can save time and space

• Immutable objects have fixed variables , Can be used safely as a constant

JDK Provided unmodifiableXXX Method

• Heavy and cumbersome

• unsafe

• Inefficient

Three ways to create immutable sets

• copyOf Method :ImmutableSet.copyOf(set)

• of Method :ImmutableSet.of("a","b","c")

• Builder Tools :ImmutableSet:builder().build()

public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();
        list.add(1);
        list.add(2);
        list.add(3);
        // use JDK Method will list Become immutable sets : This method is too cumbersome 
        List<Integer> newList = Collections.unmodifiableList(list);
        // If you modify an immutable set, you will :Exception in thread "main" java.lang.UnsupportedOperationException
        test(newList);
    }
​
​
public class UnmodifiableTest {
    public static void test(List<Integer> list){
        list.remove(0);
    }
    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();
        list.add(1);
        list.add(2);
        list.add(3);
        // use JDK Method will list Become immutable sets : This method is too cumbersome 
        List<Integer> newList = Collections.unmodifiableList(list);
        // If you modify an immutable set, you will :Exception in thread "main" java.lang.UnsupportedOperationException
        test(newList);
    }
    public void unmodifiableList(){
        ArrayList<Integer> list = new ArrayList<>();
        list.add(1);
        list.add(2);
        list.add(3);
        // The first way to create immutable sets : Create from an existing collection 
        ImmutableSet<Integer> integers1 = ImmutableSet.copyOf(list);
        // The second way to create immutable sets : Through the initial value , Create immutable collections 
        ImmutableSet<Integer> integers2 = ImmutableSet.of(1,2,3);
        // The third way to create immutable sets : adopt builder establish 
        ImmutableSet<Object> integers3 = ImmutableSet.builder().add(1).addAll(Sets.newHashSet(1, 2, 3)).build();
    }
}