Java Collections - Collections.checkedSet() Examples

package com.logicbig.example.collections;

import java.util.HashSet;
import java.util.Set;

public class CheckedSetExample {

    public static void main(String... args) {
        Set<Integer> set = new HashSet<>();
        set.add(1);
        System.out.println(set);

        Set set2 = set;
        set2.add("two");
        System.out.println(set2);
    }
}

Output

[1]
[1, two]

Using checkedSet:

package com.logicbig.example.collections;

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

public class CheckedSetExample2 {

    public static void main(String... args) {
        Set<Integer> set = new HashSet<>();
        set = Collections.checkedSet(set, Integer.class);
        set.add(1);
        System.out.println(set);

        Set set2 = set;
        set2.add("two");
        System.out.println(set2);
    }
}

Output

[1]
java.lang.ClassCastException: Attempt to insert class java.lang.String element into collection with element type class java.lang.Integer
    at java.util.Collections$CheckedCollection.typeCheck (Collections.java:3455)
    at java.util.Collections$CheckedCollection.add (Collections.java:3503)
    at com.logicbig.example.collections.CheckedSetExample2.main (CheckedSetExample2.java:22)
    at jdk.internal.reflect.DirectMethodHandleAccessor.invoke (DirectMethodHandleAccessor.java:104)
    at java.lang.reflect.Method.invoke (Method.java:565)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.executeMainMethod (AbstractExecJavaBase.java:402)
    at org.codehaus.mojo.exec.ExecJavaMojo.executeMainMethod (ExecJavaMojo.java:142)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.doExecClassLoader (AbstractExecJavaBase.java:377)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.lambda$execute$0 (AbstractExecJavaBase.java:287)
    at java.lang.Thread.run (Thread.java:1474)