Minmum depth of a tree

mindepthtree.java

// java.util.* and java.util.streams.* have been imported for this problem.
// You don't need any other imports.

public int minTreeDepth(TreeNode root) {
 
    if (root == null) {
        return 0;
    }   
    
    Queue<TreeNode> currQ = new LinkedList<TreeNode>();
    Queue<TreeNode> nextQ = new LinkedList<TreeNode>();
    currQ.add(root);
    
    int minlevel = 1;
    while(!currQ.isEmpty()) {
        
        TreeNode node = currQ.remove();
        
        if(node.left== null && node.right == null) {
            return minlevel;
        }
        
        if (currQ.isEmpty()) {
            if(node.left!=null)
                nextQ.add(node.left);
                
            if (node.right !=null)
                nextQ.add(node.right);
        
            while(!nextQ.isEmpty()) {
                currQ.add(nextQ.remove());
            }
            
            ++minlevel;
        }
        
    }
    return minlevel;
}