判断二叉树B是否是树A的子树

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
　　//判断root2是否是root1的子树
    public boolean HasSubtree(TreeNode root1,TreeNode root2) {  
        if(root1 ==null || root2==null) return false;
        
        if(isEqualTree(root1,root2)){
            return true;
        }else{       
            return HasSubtree(root1.left,root2) || HasSubtree(root1.right,root2);
        }
        
    }
　　//判断B是否是A的子树，并且从根节点开始，即A.val=B.val
    public boolean isEqualTree(TreeNode A,TreeNode B){
        if(B==null) return true;
        if(A==null) return false;

        if(A.val != B.val) return false;
        
        return isEqualTree(A.left,B.left) && isEqualTree(A.right,B.right);
        
    }
 
}