问为什么java.util.HashSet没有get(Object o)方法？

EN

package example;

import java.io.Serializable;

public class Foo implements Serializable {

    String _id;
    String _description;

    public Foo(String id){
        this._id = id
    }

    public void setDescription(String description){
        this._description = description;
    }

    public String getDescription(){
        return this._description;
    }

    public boolean equals(Object obj) {
        //equals code, checks if id's are equal
    }

    public int hashCode() {
        //hash code calculation
    }

}

package example;

import java.util.HashSet;

public class Example {

    public static void main(String[] args){
        HashSet<Foo> set = new HashSet<Foo>();

        Foo foo1 = new Foo("1");
        foo1.setDescription("Number 1");

        set.add(foo1);
        set.add(new Foo("2"));

        //I want to get the object stored in the Set, so I construct a object that is 'equal' to the one I want.
        Foo theFoo = set.get(new Foo("1")); //Is there a reason this is not allowed?
        System.out.println(theFoo.getDescription); //Should print Number 1
    }

}