Basic HashMap

We need to implement equals and hashCode when we create new class as a hash key

    public static class SampleClass {
        public int i;
        public int j;

        public SampleClass(int i, int j) {
            this.i = i;
            this.j = j;
        }

        @Override
        public boolean equals(Object o) {
            if(this == o) {
                return true;
            }

            if(o == null || getClass() != o.getClass()) {
                return false;
            }

            SampleClass smpl = (SampleClass)o;

            return i == smpl.i && j == smpl.j;
        }

        @Override
        public int hashCode() {
            return i * 10 + j;
        }
    }