public class Test {

    private int id;
    private int age;

    public Test(int id, int age) {
        this.id = id;
        this.age = age;
    }

    public boolean equals(Object o) {
        Test otherTest = (Test) o;
        return otherTest.id == this.id;
    }

    public String toString() {
        return "айди  - " + this.id;
    }

    @Override
    public int hashCode() {
        return this.id * 12345;
    }
}