int count = 150;
int[] num = new int[count];
for (int i=0; i<count; i++) { //生成随机数
    num[i] = (int)(Math.random()*10);
}
Map<Integer, Integer> map = new LinkedHashMap<Integer, Integer>();
for (int i=0, j=0; i<count; i++) { //寻找最大距离
    if (! map.containsKey(num[i])) {
        for (j=count-1; j>=i; j--) {
            if (num[j] == num[i]) {
                map.put(num[i], j-i-1);
                break;
            }
        }
        if (j<i) map.put(num[i], 0);
    }
}

for (Map.Entry<Integer, Integer> e : map.entrySet()) { //打印结果
    System.out.printf("%s的最大距离%s\n", e.getKey(), e.getValue());
}

------解决方案--------------------
Java code

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;


public class Test{
    public static void test(int count,int randomNum){
        int[] data = new int[count];
        for (int i=0; i<count; i++) { //生成随机数
            data[i] = (int)(Math.random()*randomNum);
        }
        System.out.println(Arrays.toString(data));
        Map<Integer,Integer[]> map = new HashMap<Integer,Integer[]>();
        for(int i=0;i<count;i++){
            int key = data[i];
            if(map.containsKey(data[i])){
                Integer[] temp =map.get(key);
                temp[1] = i-temp[0];
                map.put(key,temp);
            }
            else{
                map.put(key,new Integer[]{i,0});
            }
        }
        
        for (Map.Entry<Integer, Integer[]> e : map.entrySet()) { //打印结果
            System.out.printf("%s的最大距离%s\n", e.getKey(), e.getValue()[1]);
        }
    }
    public static void main(String[] args) {
        test(10,5);
        test(150,10);
    }
}

------解决方案--------------------
用两个伴随数组遍历一次就行了

Java code

import java.util.Arrays;
import java.util.Random;


public class Test2 {
    static final int COUNT = 15;
    static int[] mArr = new int[COUNT];
    
    public static void main(String[] args) {
        //产生随机数
        Random random = new Random();
        for(int i = 0;i < COUNT;i++)
            mArr[i] = random.nextInt(10);
        //获取最大距离
        int[] pos = new int[10];
        for(int i = 0;i < pos.length;i++){
            pos[i] = -1;
        }
        int[] dis = new int[10];
        for(int i = 0;i < COUNT;i++){
            if(pos[mArr[i]] != -1)
                dis[mArr[i]] += (i - pos[mArr[i]] - 1);
            pos[mArr[i]] = i;
        }
        //输出
        //System.out.println(Arrays.toString(mArr));
        for(int i = 0;i < dis.length;i++){
            if(dis[i] != 0)
                System.out.println(i + " 最长距离:" + dis[i]);
        }
    }

}

------解决方案--------------------
生成随机数的楼上几位都写的，这里我就不写了直接遍历
Java code

/**
     * 遍历一次获得最大距离
     * @param num
     * @param data
     * @return
     */
    public static int test3(int[] num,int data){
        int count=0;        //计数1
        int count2=0;        //当遍历到相同的数值是计数加1
        int count3=0;        //最大长度
        boolean flag=true;    //是否首次匹配
        for(int i=0;i<num.length;i++){
            if(data==num[i]){    //如果匹配成功
                if(flag){
                    flag=false;    //设置为非首次
                }else{
                    count3+=count;
                    count=0;
                    count2++;
                    continue;
                }
            }
            if(!flag){
                if(data!=num[i]){
                    count++;
                }
            }
        }
        count3+=count2-1;
        System.out.println("count3:"+count3);
        return count;
    }

    public static void main(String[] args) throws Exception {
        int [] num ={2,4,2,7,6,9,2,6,8}; 
        test3(num,2);
    }