/**
  * List的toString方法，結(jié)果前后會(huì)帶有英文的中括號(hào)[]，如：[1, 2, 3, 4, 5]
  */
public static void main(String[] args) {
   List<Integer> asList = Arrays.asList(1, 2, 3, 4, 5);
   
   String list2String = asList.toString();
   System.out.println(list2String);
   //使用replaceAll方法替換 中括號(hào)
   list2String = list2String.replaceAll("\\[|]", "");
   System.out.println(list2String);
}

public class Demo2 {

    /**
     * List 轉(zhuǎn) String
     * stream流中的Collections.joining方法
     **/
    public static void main(String[] args) {
        List<String> list = Arrays.asList("張三", "李四", "王武", null, "麻子");
        //java stream流中的Collections.joining方法
        //指定分隔符
        String collect = list.stream().collect(Collectors.joining(","));
        //沒(méi)有分隔符，直接拼接
        String collect1 = list.stream().collect(Collectors.joining());
        //指定分隔符，前綴，后綴
        String collect2 = list.stream().collect(Collectors.joining(",", "{", "}"));
        System.out.println(collect);//張三,李四,王武,null,麻子
        System.out.println(collect1);//張三李四王武null麻子
        System.out.println(collect2);//{張三,李四,王武,null,麻子}
    }
}

   /**
     * String.join()
     **/
    public static void main(String[] args) {
        List<String> list = Arrays.asList("張三", "李四", "王武", null, "麻子");
        String join = String.join(",", list);
        System.out.println(join);//張三,李四,王武,null,麻子
    }

   /**
     * StringUtils.join()
     **/
    public static void main(String[] args) {
        List<String> list = Arrays.asList("張三", "李四", "王武", null, "麻子");
        //StringUtils.join方法，集合中有null的話(huà)，會(huì)轉(zhuǎn)成空串""
        String join = StringUtils.join(list, ",");
        System.out.println(join); //張三,李四,王武,,麻子
    }

   /**
     * StringBuilder、StringBuffer的append()方法
     **/
    public static void main(String[] args) {
        List<String> list = Arrays.asList("張三", "李四", "王武", null, "麻子");
        //3. StringBuilder、StringBuffer的append方法自定義join方法
        StringBuilder sb = new StringBuilder();
        for (String s : list) {
            sb.append(s).append(",");
        }
        //sb.insert(0, "join如下：");
        if (sb.length() > 1) {
            sb.deleteCharAt(sb.length() - 1);
        }
        System.out.println(sb.toString()); //張三,李四,王武,null,麻子
    }

public class Demo2 {

    public static class ListJoin<E> {

        public String join(String delimiter, Collection<? extends E> list) {
            Objects.requireNonNull(delimiter);
            Objects.requireNonNull(list);
            StringBuilder result = new StringBuilder();
            for (E obj : list) {
                //根據(jù)需要對(duì)空進(jìn)行處理
                if (Objects.isNull(obj)) {
                    continue;
                }
                result.append(obj).append(delimiter);
            }
            if (result.length() > 1) {
                result.deleteCharAt(result.length() - 1);
            }

            return result.toString();
        }
    }

    /**
     * StringBuilder、StringBuffer的append()方法
     **/
    public static void main(String[] args) {
        List<String> list = Arrays.asList("張三", "李四", "王武", null, "麻子");
        //上述join方法可以修改成通用的join方法
        ListJoin<String> strDemo = new ListJoin<>();
        String join = strDemo.join(",", list);
        System.out.println(join); //張三,李四,王武,麻子

        ListJoin<Integer> intDemo = new ListJoin<>();
        List<Integer> asList = Arrays.asList(1, 2, 3, 4, 5);
        String intJoin = intDemo.join("-", asList);
        System.out.println(intJoin); //1-2-3-4-5
    }
}

public String toString() { 
return getClass().getName() +"@"+Integer.toHexString(hashCode()); //打印類(lèi)的全命名+內(nèi)存地址
} 

public String toString(){ 
     return "name:" + this.name+ ", pwd:"+this.pwd;
    //這里才是你要返回的值 如果沒(méi)復(fù)寫(xiě)則調(diào)用Object類(lèi)中的toString()方法,所以具體輸出形式自己定
        }