Java中list泛型插入int或者String字符串并排序

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向String泛型集合中插入5个字符串，并排序。看代码

public class TestList {    public void TestStringList() {        List<String> stringList = new ArrayList<String>();        stringList.add("baidu");        stringList.add("yahoo");        stringList.add("360");        stringList.add("bing");        stringList.add("google");        System.out.println("排序前:");        for (String string : stringList) {            System.out.print(string + "   ");        }        Collections.sort(stringList);        System.out.println("\n升序后:");        for (String string : stringList) {            System.out.print(string + "   ");        }        Collections.reverse(stringList);        System.out.println("\n降序后:");        for (String string : stringList) {            System.out.print(string + "   ");        }    }}

在main方法中调用，并打印出结果

public static void main(String[] args) {        TestList t = new TestList();        t.TestStringList();}

看结果

排序前:baidu   yahoo   360   bing   google   升序后:360   baidu   bing   google   yahoo   降序后:yahoo   google   bing   baidu   360

注意了：排序是按照：数字——大写——小写的顺序执行的。
改进代码，插入的字符串是程序运行时添加并且不重复的。

/**     * 在Character 泛型中添加元素     * @param charList     * @param beg 开始     * @param end 结束     */    public void addAlphabet(List<Character> charList, char beg, char end) {        for (char c = beg; c <= end; c++) {            charList.add(c);        }    }

然后再添加数据

public void insertStringList() {        List<String> strList = new ArrayList<String>();        List<Character> charList = new ArrayList<Character>();        // 将数字和字母烦人你别加入        addAlphabet(charList, '0', '9');        addAlphabet(charList, 'a', 'z');        addAlphabet(charList, 'A', 'Z');        // 随机数        Random random = new Random();        for (int i = 0; i < 5; i++) {            // 随机生成的字符串            String str = "";            for (int j = 0; j < 10; j++) {                do {                    int index = random.nextInt(62);                    str = str + charList.get(index);                } while (strList.contains(str));            }            strList.add(str);        }        System.out.println("排序前:");        for (String string : strList) {            System.out.print(string + "   ");        }        Collections.sort(strList);        System.out.println("\n升序后:");        for (String string : strList) {            System.out.print(string + "   ");        }        Collections.reverse(strList);        System.out.println("\n降序后:");        for (String string : strList) {            System.out.print(string + "   ");        }    }

打印结果如下：

排序前:BhD4dljaF9   zyYbuIAAmH   Ruvcdp13Aq   dZZmF9kKmh   dumBvqhZji   升序后:BhD4dljaF9   Ruvcdp13Aq   dZZmF9kKmh   dumBvqhZji   zyYbuIAAmH   降序后:zyYbuIAAmH   dumBvqhZji   dZZmF9kKmh   Ruvcdp13Aq   BhD4dljaF9

再次修改代码将生成的字符串的长度提取为方法

/**     * @param newLength 要生成的字符串的长度     * @return 生成的字符串     */    public  String getRandomString(int newLength){        StringBuffer buffer=new StringBuffer("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");        StringBuffer newBuffer=new StringBuffer();        Random random=new Random();        int range=buffer.length();        for (int i = 0; i <newLength; i++) {            newBuffer.append(buffer.charAt(random.nextInt(range)));        }        return newBuffer.toString();    }

调用上面的方法

public void getStringList(){        List<String> strList=new ArrayList<String>();        String str="";        for (int i = 0; i < 5; i++) {                   do {                 str = getRandomString(10);            } while (strList.contains(str));                strList.add(str);        }        System.out.println("排序前:");        for (String string : strList) {            System.out.print(string + "   ");        }        Collections.sort(strList);        System.out.println("\n升序后:");        for (String string : strList) {            System.out.print(string + "   ");        }        Collections.reverse(strList);        System.out.println("\n降序后:");        for (String string : strList) {            System.out.print(string + "   ");        }    }

当然这里生成int类型的整数的方法也大致如此。如下，生成1000以内的随机数8个

public void getInteger(){        List<Integer> list=new ArrayList<Integer>();        //随机数        Random random=new Random();        int i;        for (int j = 0; j <8; j++) {            do {                i = random.nextInt(1000);            } while (list.contains(i));            list.add(i);        }        System.out.println("排序前:");        for (Integer integer : list) {            System.out.print(integer+"  ");        }        Collections.sort(list);        System.out.println("\n升序后:");        for (Integer integer : list) {            System.out.print(integer+"  ");        }        Collections.reverse(list);        System.out.println("\n降序后:");        for (Integer integer : list) {            System.out.print(integer+"  ");        }    }

好了，就写到这里。

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