问如何为MySQL表创建高效索引？

ListIterationExample.java

import java.util.*;

public class ListIterationExample {

     public static void main(String []args){

        List<Integer> numbers = new ArrayList<Integer>();

        // populates list with initial values

        for (Integer i : Arrays.asList(0,1,2,3,4,5,6,7))

            numbers.add(i);

        printList(numbers);         // 0,1,2,3,4,5,6,7

        // replaces each element with twice its value

        for (int index=0; index < numbers.size(); index++) {

            numbers.set(index, numbers.get(index)*2); 

        }

        printList(numbers);         // 0,2,4,6,8,10,12,14

        // does nothing because list is not being changed

        for (Integer number : numbers) {

            number++; // number = new Integer(number+1);

        }

        printList(numbers);         // 0,2,4,6,8,10,12,14  

        // same as above -- just different syntax

        for (Iterator<Integer> iter = numbers.iterator(); iter.hasNext(); ) {

            Integer number = iter.next();

            number++;

        }

        printList(numbers);         // 0,2,4,6,8,10,12,14

        // ListIterator<?> provides an "add" method to insert elements

        // between the current element and the curso

        for (ListIterator<Integer> iter = numbers.listIterator(); iter.hasNext(); ) {

            Integer number = iter.next();

            iter.add(number+1);     // insert a number right before this

        }

        printList(numbers);         // 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15

        // Iterator<?> provides a "remove" method to delete elements

        // between the current element and the curso

        for (Iterator<Integer> iter = numbers.iterator(); iter.hasNext(); ) {

            Integer number = iter.next();

            if (number % 2 == 0)    // if number is even 

                iter.remove();      // remove it from the collection

        }

        printList(numbers);         // 1,3,5,7,9,11,13,15

        // ListIterator<?> provides a "set" method to replace elements

        for (ListIterator<Integer> iter = numbers.listIterator(); iter.hasNext(); ) {

            Integer number = iter.next();

            iter.set(number/2);     // divide each element by 2

        }

        printList(numbers);         // 0,1,2,3,4,5,6,7

     }

     public static void printList(List<Integer> numbers) {

        StringBuilder sb = new StringBuilder();

        for (Integer number : numbers) {

            sb.append(number);

            sb.append(",");

        }

        sb.deleteCharAt(sb.length()-1); // remove trailing comma

        System.out.println(sb.toString());

     }

}

for (E element : list) {

    . . .

}