Java遍历对象列表

Question

I'm a beginner in Java Programming and having hard time understand the concept of loop through list of objects in Java.

Input data records are of the form:

    TestDataSet1 |4|01-category1|100|43|||
    TestDataSet2 |4|02-category2|10044307001|0|100|2016-07-20 21:36:00|
    TestDataSet3 |4|03-category3|104331|
    TestDataSet4 |5|04-category4|100|2016-07-20 21:36:00|
    TestDataSet5 |4|01-category1|100|43|||
    TestDataSet3 |4|03-category3|104331|

In order to read the above records data in my program based on category, created of list of objects for each category as:

List<Object> category1Orcategory2OrCategory3OrCategory4;

If input data is of the form,

TestDataSet1 |4|01-category1|100|43|||
TestDataSet2 |4|02-category2|10044307001|0|100|2016-07-20 21:36:00|
TestDataSet3 |4|03-category3|104331|
TestDataSet4 |4|04-category4|100|2016-07-20 21:36:00|

accessing list of objects can be done with:

 Category1 - object.getcategory1Orcategory2OrCategory3OrCategory4().get(0);
 Category2 - object.getcategory1Orcategory2OrCategory3OrCategory4().get(1);
 Category3 - object.getcategory1Orcategory2OrCategory3OrCategory4().get(2);
 Category4 - object.getcategory1Orcategory2OrCategory3OrCategory4().get(3);

So, looping can be done as:

 for(int index=0 ; index = list.size(); index++){
 object.getcategory1Orcategory2OrCategory3OrCategory4().get(index);
 }

But at times, some of the category data will be missing and input will look like:

case1: 
TestDataSet1 |4|01-category1|100|43|||
TestDataSet3 |4|03-category3|104331|
TestDataSet4 |5|04-category4|100|2016-07-20 21:36:00|

or

case2:
TestDataSet1 |4|01-category1|100|43|||
TestDataSet3 |4|02-category2|104331|
TestDataSet4 |5|04-category4|100|2016-07-20 21:36:00|

It is understandable that in case1 the data can be accessed in :

 Category1 - object.getcategory1Orcategory2OrCategory3OrCategory4().get(0);
 Category3 - object.getcategory1Orcategory2OrCategory3OrCategory4().get(1);
 Category4 - object.getcategory1Orcategory2OrCategory3OrCategory4().get(2);

or in case2:

 Category1 - object.getcategor1Orcategory2OrCategory3OrCategory4().get(0);
 Category2 - object.getcategory1Orcategory2OrCategory3OrCategory4().get(1);
 Category4 - object.getcategory1Orcategory2OrCategory3OrCategory4().get(2);

I'm confused on how can I make the 'for loop' generic to cover all these cases in looping through the list of objects:

 for(int index=0 ; index = list.size(); index++){
 object.getcategory1Orcategory2OrCategory3OrCategory4().get(???);
 }

Answer 1

Your data seems to be a | -separated text file, with up to 8 values per row, so you create a class, eg called DataSet , with 8 fields, then create a list of those for storing the rows, ie List<DataSet> .

You can then loop the list using an enhanced for statement:

for (DataSet dataSet : list) {
    // now get values with calls like list.getName()
}