Java char int 转换/char[]char数组 字符串 转换 String.valueOf/Arrays.sort/int[]数组初始0/Integer[]数组初始null

Posted 2022-06-18 二十六画生的博客

    public static void main(String[] args) 
        int[] crr = new int[200];
        char a = 'a';
        System.out.println(crr[a]);//0
        System.out.println(crr[a]--);//0
        System.out.println(crr[a] + 2);//1

        

        int[] arr = new int[10];//初始化正确

        System.out.println(arr[0]);//0
        System.out.println(arr[0] + 1);//1
        System.out.println(arr[0] - 1);//-1
        System.out.println('b' - 'a');//1

        Integer[] bArr = new Integer[10];//初始化正确
        System.out.println(bArr[0]);//null
        //System.out.println(bArr[0]++);//NullPointerException
        //System.out.println(bArr[0]--);//NullPointerException

        Integer[] cArr = new Integer[]1, 2;//初始化正确
        //Integer[] dArr = new Integer[2]1,2;//报错

        

        char c = 'c';
        System.out.println(c);//c
        System.out.println((int) c);//99
        int cint = c;
        System.out.println(cint);//99

        

        String s = "askcbd";

        char[] sarr = s.toCharArray();
        System.out.println(sarr);//askcbd

        Arrays.sort(sarr);//返回void
        System.out.println(sarr);//abcdks

        String s2 = new String(sarr);
        System.out.println(s2);//abcdks

        String s3 = String.valueOf(sarr);
        System.out.println(s3);//abcdks