Search a 2D Matrix -- LeetCode

public boolean searchMatrix(int[][] matrix, int target) {
    if(matrix == null || matrix.length==0 || matrix[0].length==0)
        return false;
    int l = 0;
    int r = matrix.length-1;
    while(l<=r)
    {
        int mid = (l+r)/2;
        if(matrix[mid][0] == target) return true;
        if(matrix[mid][0] > target)
        {
            r = mid-1;
        }
        else
        {
            l = mid+1;
        }
    }
    int row = r;
    if(row<0)
        return false;
    l = 0;
    r = matrix[0].length-1;
    while(l<=r)
    {
        int mid = (l+r)/2;
        if(matrix[row][mid] == target) return true;
        if(matrix[row][mid] > target)
        {
            r = mid-1;
        }
        else
        {
            l = mid+1;
        }
    }   
    return false;
}