Solution.java

class Solution {
    public boolean checkSubTree(TreeNode t1, TreeNode t2) {
        if (t2 == null)
            return true;
        if (t1 == null)
            return false;
        return isSubTree(t1, t2) || checkSubTree(t1.left, t2) || checkSubTree(t1.right, t2);
    }

    public boolean isSubTree(TreeNode t1, TreeNode t2){
        if (t2 == null)
            return true;
        if (t1 == null)
            return false;
        if (t1.val != t2.val)
            return false;
        return isSubTree(t1.left,t2.left) && isSubTree(t1.right,t2.right);
    }
}