coding bat for loops III: loop harder

1)Given a string, return a string made of the chars at indexes 0,1, 4,5, 8,9 ... so "kittens" yields "kien".

altPairs("kitten") → "kien"
altPairs("Chocolate") → "Chole"
altPairs("CodingHorror") → "Congrr

public String altPairs(String str) {
int a = 0;
String bricks = "";
for(int i = 0;i <str.length();i++){
  if(a == 0 || a == 1){
    bricks += str.substring(i,i+1);
  }else if(a == 3){
  a = -1;
  }
  a++;
}
return bricks;
}

2)Given an array of ints, return the number of times that two 6's are next to each other in the array. Also count instances where the second "6" is actually a 7.

array667({6, 6, 2}) → 1
array667({6, 6, 2, 6}) → 1
array667({6, 7, 2, 6}) → 1

public int array667(int[] nums) {
  int a = 0;
  for(int i = 0;i < nums.length -1; i++){
    if (nums[i] == 6 &&(nums[i+1] == 6 || nums[i+1] == 7)){
    a += 1;
    }
  }
  return a;
}

3)Given an array of ints, we'll say that a triple is a value appearing 3 times in a row in the array. Return true if the array does not contain any triples.

noTriples({1, 1, 2, 2, 1}) → true
noTriples({1, 1, 2, 2, 2, 1}) → false
noTriples({1, 1, 1, 2, 2, 2, 1}) → false

public boolean noTriples(int[] nums) {
  for(int i = 0; i < nums.length-2;i++){
    if (nums[i] == nums[i+1] && nums[i] == nums[i+2]){
      return false;
    }
  }
  return true;
}

4)