Implementing Array Algorithms Practice Test

public static int firstIndex(int[] a,int target){
  int lo=0, hi=a.length-1, ans=-1;
  while(lo<=hi){
    int mid=(lo+hi)/2;
    if(a[mid]==target){ ans=mid; hi=mid-1; }
    else if(a[mid]<target) lo=mid+1;
    else hi=mid-1;
  }
  return ans;
}

public static int firstIndex(int[] a,int target){
  int lo=0, hi=a.length;
  int ans=-1;
  while(lo<=hi){
    int mid=(lo+hi)/2;
    if(a[mid]>=target){ ans=mid; hi=mid-1; }
    else lo=mid+1;
  }
  return (a[ans]==target)? ans : -1;
}

public static int firstIndex(int[] a,int target){
  int lo=0, hi=a.length-1, ans=-1;
  while(lo<=hi){
    int mid=(lo+hi)/2;
    if(a[mid]==target){ ans=mid; lo=mid+1; }
    else if(a[mid]<target) lo=mid+1;
    else hi=mid-1;
  }
  return ans;
}

public static int firstIndex(int[] a,int target){
  int lo=0, hi=a.length-1;
  while(lo<=hi){
    int mid=(lo+hi)/2;
    if(a[mid]==target) return mid;
    if(a[mid]<target) lo=mid+1; else hi=mid-1;
  }
  return -1;
}