Java实现向数组里添加元素

        String[] str = new String[5];
        System.out.println(Arrays.toString(str));
        String[] str2 = new String[]{"a", "b"};
        System.out.println(Arrays.toString(str2));
        String[] str3 = {"c", "d"};
        System.out.println(Arrays.toString(str3));

        String[] datecolumn = {"Mon", "Tue", "Wed"};
        /**
         * 重新创建一个新的数组，需要添加多少个元素，就在原来的数组长度的基础上加几
         */
        System.out.println(datecolumn.length);
        String[] newColume = new String[datecolumn.length + 1];
        for (int i = 0; i < datecolumn.length; i++) {
            newColume[i]=datecolumn[i];
        }
        newColume[datecolumn.length]="Thu";
        System.out.println(Arrays.toString(newColume));

        List<String> datelist = new ArrayList<String>();
        datelist.add("Mon");
        datelist.add("Tue");
        datelist.add("Wed");
        //因为数组下标是从0开始，这里add的index为2即为第三个元素
        datelist.add(2, "Thu");
        datelist.add(1, "Fri");
        System.out.println(datelist);

        //1.已有的数组datecolumn和list集合
        String[] datecolumn = {"Mon", "Tue", "Wed"};
        List<String> list = new ArrayList<>();
        list.add("Thu");
        list.add("Fri");
        list.add("Sat");
        list.add("Sun");

        //2.数组和集合add到titleList中
        List<String> titleList = new ArrayList<String>();
        //将datecolum数组转换list并add到titleList中
        titleList.addAll(Arrays.asList(datecolumn));
        //将list添加到titleList中
        titleList.addAll(list);

        //3.titleList集合转换title数组
        String[] title = titleList.toArray(new String[titleList.size()]);
        //4.遍历title数组
        for (String string : title) {
            System.out.println(string);
        }