How to get unique random numbers in java

We know that Random random = new Random() may get repeated random numbers

So suppose you want to get between 1 and 33 What should we do with six non-repeating random numbers?

Example:

//首先定义一个数字数组存储1到33
int[ ]  redBall = new int[33[;
for(int i = 0;i<redBall.length;i++){
　　redBall[i] = i+1;
}
int[ ]  redNumber = new int[6];     //存储六个随机数的实际数组
int index = -1;                             //通过随机数字数组下标获取随机数
for(int i = 0;i<redNumber.length;i++){
　　index = random.nextInt(redBall.length-i);   //每次获取数字数组长度-i的随机数，比如第一次循环为33第二次为32，
　　redNumber[i] = redBall[index];                   //把数字数组随机下标的值赋给实际数组
　　int temp = redBall[index];                           //定义一个变量暂存下标为index时的值
　　redBall[index] = redBall[redBall.length-1-i];  //把下标为index的值与数组下标最后的值交换
　　redBall[redBall.length-1-i] = temp;             //交换后，下次循环把数字数组最后的值去掉，从而实现不重复
}

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