Android generates local verification code decomposition

1. Select any four characters from a character array

char[] charArr={"a","b","c","d"};
StringBuilder sb= new StringBuilder();
Random rd = new Random();
for(int i=0;i<4;i++){
    sb.append(charArr[rd.nextInt(charArr.length)]);
}

2. Randomly generate a color

Random rd = new Random();

int r=rd.nextInt(256);

int g=rd.nextInt(256);
int b=rd.nextInt(256);
int color = Color.rgb(r,g,b);