Java Random randomFromIterator(Iterator iter)

Description

random From Iterator

License

Apache License

Declaration

public static <T> T randomFromIterator(Iterator<T> iter) 

Method Source Code

//package com.java2s;
/*/*  w  w w .  j a v a  2 s .  c o m*/
Copyright (c) 2012 IBM Corp.
    
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
    
http://www.apache.org/licenses/LICENSE-2.0
    
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import java.util.*;

public class Main {
    public static <T> T randomFromIterator(Iterator<T> iter) {
        if (!iter.hasNext()) {
            return null;
        }
        T element = iter.next();
        double seen = 1;
        while (iter.hasNext()) {
            seen += 1;
            T posReplace = iter.next();
            if (Math.random() < 1.0 / seen) {
                element = posReplace;
            }
        }
        return element;
    }
}

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