How to solve Java array, character and arithmetic sequence problems

class Solution {
    public int[] relativeSortArray(int[] arr1, int[] arr2) {
        int[] arr = new int[1001];
        int[] ans = new int[arr1.length];
        int index = 0;
        for(int i =0;i<arr1.length;i++){
            arr[arr1[i]]+=1;
        }
        for(int i = 0;i<arr2.length;i++){
            while(arr[arr2[i]]>0){
                arr[arr2[i]]--;
                ans[index] = arr2[i];
                index++;
            }
        }
        for(int i =0;i<arr.length;i++){
            if(arr[i]!=0){
                for(int j =0;j<arr[i];j++){
                    ans[index] = i;
                    index++;
                }
            }
        }
        return ans;
    }
}

class Solution {
    public int findLucky(int[] arr) {
        int[] nums = new int[500];
        for(int i =0;i<arr.length;i++){
            nums[arr[i]]+=1;
        }
        int max = -1;
        for(int i = 1;i<nums.length;i++){
            if(i == nums[i]){
                max = Math.max(max,i);
            }
        }
        return max;
    }
}

class Solution {
    public int maxPower(String s) {
        if(s.length()==1) return 1;
        int left = 1;
        int max = Integer.MIN_VALUE;
        int con = 1;
        while(left<s.length()){
            if(s.charAt(left)==s.charAt(left-1)){
                con++;
                max = Math.max(con,max);
            }else{
                max = Math.max(con,max);
                con = 1;
            }
            left++;
        }
        return max;
    }
}

class Solution {
    public boolean canMakeArithmeticProgression(int[] arr) {
        Arrays.sort(arr);
        int num = arr[1]-arr[0];
        
        for(int i = 1;i<arr.length;i++){
            if(arr[i]-arr[i-1]==num){
                continue;
            }else{
                return false;
            }
        }
        return true;
    }
}