[MINOR] Remove unnecessary check in MLSerDe

## What changes were proposed in this pull request?
1, remove unnecessary `require()`, because it will make following check useless.
2, update the error msg.

## How was this patch tested?
no test

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #14972 from zhengruifeng/del_unnecessary_check.

1 files changed, 4 insertions, 5 deletions

diff --git a/mllib/src/main/scala/org/apache/spark/ml/python/MLSerDe.scala b/mllib/src/main/scala/org/apache/spark/ml/python/MLSerDe.scala
index 1279c901c5..4b805e1454 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/python/MLSerDe.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/python/MLSerDe.scala
@@ -56,9 +56,8 @@ private[spark] object MLSerDe extends SerDeBase with Serializable {
     }
 
     def construct(args: Array[Object]): Object = {
-      require(args.length == 1)
       if (args.length != 1) {
-        throw new PickleException("should be 1")
+        throw new PickleException("length of args should be 1")
       }
       val bytes = getBytes(args(0))
       val bb = ByteBuffer.wrap(bytes, 0, bytes.length)
@@ -95,7 +94,7 @@ private[spark] object MLSerDe extends SerDeBase with Serializable {
 
     def construct(args: Array[Object]): Object = {
       if (args.length != 4) {
-        throw new PickleException("should be 4")
+        throw new PickleException("length of args should be 4")
       }
       val bytes = getBytes(args(2))
       val n = bytes.length / 8
@@ -143,7 +142,7 @@ private[spark] object MLSerDe extends SerDeBase with Serializable {
 
     def construct(args: Array[Object]): Object = {
       if (args.length != 6) {
-        throw new PickleException("should be 6")
+        throw new PickleException("length of args should be 6")
       }
       val order = ByteOrder.nativeOrder()
       val colPtrsBytes = getBytes(args(2))
@@ -187,7 +186,7 @@ private[spark] object MLSerDe extends SerDeBase with Serializable {
 
     def construct(args: Array[Object]): Object = {
       if (args.length != 3) {
-        throw new PickleException("should be 3")
+        throw new PickleException("length of args should be 3")
       }
       val size = args(0).asInstanceOf[Int]
       val indiceBytes = getBytes(args(1))