Minsum and maxsum in a given Binary Tree

public static int maxSum(BinaryTree root,int maxsum){
maxsum = maxsum + root.value;
if(root==null)
return 0;
if(root.left==null && root.right==null){
return maxsum;
}
return(Math.max(maxSum(root.left,maxsum),maxSum(root.right,maxsum)));
}

public static int minSum(BinaryTree root,int minsum){
minsum = minsum + root.value;
if(root==null)
return 0;
if(root.left==null && root.right==null){
return minsum;
}
return(Math.min(minSum(root.left,minsum),minSum(root.right,minsum)));
}