Collections.sort()方法，字元排序

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;

public class CollectionsTest {
    public void testSort3() {
        StringBuilder st = new StringBuilder();//構建StringBuilder類
        List stringlist = new ArrayList();
        String str = "0123456789abcdefghijklmnobqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
        for (int i = 0; i