[SPARK-11723][ML][DOC] Use LibSVM data source rather than MLUtils.loadLibSVMFile to load DataFrame

Use LibSVM data source rather than MLUtils.loadLibSVMFile to load DataFrame, include:
* Use libSVM data source for all example codes under examples/ml, and remove unused import.
* Use libSVM data source for user guides under ml-*** which were omitted by #8697.
* Fix bug: We should use ```sqlContext.read().format("libsvm").load(path)``` at Java side, but the API doc and user guides misuse as ```sqlContext.read.format("libsvm").load(path)```.
* Code cleanup.

mengxr

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #9690 from yanboliang/spark-11723.

1 files changed, 2 insertions, 2 deletions

diff --git a/docs/ml-linear-methods.md b/docs/ml-linear-methods.md
index 16e2ee7129..85edfd3734 100644
--- a/docs/ml-linear-methods.md
+++ b/docs/ml-linear-methods.md
@@ -95,7 +95,7 @@ public class LogisticRegressionWithElasticNetExample {
     String path = "data/mllib/sample_libsvm_data.txt";
 
     // Load training data
-    DataFrame training = sqlContext.read.format("libsvm").load(path);
+    DataFrame training = sqlContext.read().format("libsvm").load(path);
 
     LogisticRegression lr = new LogisticRegression()
       .setMaxIter(10)
@@ -292,7 +292,7 @@ public class LinearRegressionWithElasticNetExample {
     String path = "data/mllib/sample_libsvm_data.txt";
 
     // Load training data
-    DataFrame training = sqlContext.read.format("libsvm").load(path);
+    DataFrame training = sqlContext.read().format("libsvm").load(path);
 
     LinearRegression lr = new LinearRegression()
       .setMaxIter(10)