I don’t quite understand what you meant by your first paragraph...

My understanding is: Is there any convenient tool that can achieve your needs?

Yes, the most indispensable thing about Java is tools. Basically, as long as you think of the tools you need, search online, and you can find them in 99% of the cases.

It is recommended to usejava8+google guava, it can be used in any combination, it is better to use both at the same time.

Based on the situations you mentioned in these 3 examples, here are the answers one by one:

Q: Two element sets. Find the empty element at the same position in the corresponding other set
A: First, it is recommended to write a zip method to mergedescArray和codeListinto an object array, and then operate on the object array.

public static  List> zip(List list1, List list2) throws IllegalArgumentException { if (list1 == null || list2 == null || list1.size() != list2.size()) { throw new IllegalArgumentException("Two list must have the same size"); } List> results = Lists.newArrayListWithCapacity(list1.size()); for (int i = 0; i < list1.size(); ++i) { // Explicit type parameter just because eclipse is not cool // noinspection RedundantTypeArguments Pair pair = Pair.of(list1.get(i), list2.get(i)); results.add(pair); } return results; }

Then:

List> empytCodeList = zip(codeList, descList).stream() .filter(v -> Objects.isNull(v.getFirst()))// 找出codeList中为空的对象 .collect(Collectors.toList());

Q: A set is associated with a Map through another set and generates a new Map

A: In the same way, first zip the two arrays into object arrays, then:

Map codeCountMap = zip(codeList, descList).stream() .collect(Collectors.toMap(Pair::getFirst, v -> descCouponInfoMap.get(v.getSecond()).getCount()));//这里有个隐患就是map.get(desc)有可能未null，从而引发空指针

Q: Each of the two object lists extracts an attribute to form a Map

A: In the same way, first zip the two arrays into object arrays, then:

Map descCodeMap = zip(fooList, barList).stream() .collect(Collectors.toMap(v -> v.getFirst().getDesc(), v -> v.getSecond().getCode()));

You mentioned dynamically obtaining attribute values. Before java8, you could dynamically obtain attribute values through reflection. In java8, you could obtain them through method references. Here I take java8 as an example:

public static void getFieldVal(Supplier supplier) { return supplier.get(); }

couponInfo::getCount就是一个supplier, based on this principle, many functions that could only be realized through reflection in the past can be realized in java8 throughmethod reference.

The above, even if you don’t use Java8, you can use guava to elegantly implement these functions.

Reference:

1. http://ifeve.com/google-guava/

2. http://www.importnew.com/1036...

3. http://www.importnew.com/1190...

In fact, Java 8 does not require zip,

import java.util.*; import java.util.stream.*;

Find the corresponding collection that is empty

List result = IntStream.range(0, descArray.length) .filter(i -> codeList.get(i) == null) .mapToObj(i -> descArray[i]) .collect(Collectors.toList());

Related Map

Map codeCountMap = IntStream.range(0, descArray.length) .boxed() .collect(Collectors.toMap( i -> codeList.get(i), i -> descCouponInfoMap.get(descArray[i]).getCount()));

Generate Map

Map descCodeMap = IntStream.range(0, descArray.length) .boxed() .collect(Collectors.toMap( i -> descArray[i], i -> codeList.get(i)));

Obviously this is your problem.
Do you know what classes and objects are?
Using list map for everything is of course not possible.
You define a coupon class with code and desc attributes
List ticketList;
for(Ticket ticket:ticketList){
if(ticket.getCode()==null){

System.out.println(ticket.getDesc());

}
}

I won’t mention the second and third ones.

The shortcomings of high-rise design cannot be made up for by the bottom floor.

The poster needs to strengthen abstract design and data structure design.
The first scene is a very unstable design based on position. There should be a specific type

class Coupon { int id; //对应位置，保证不重复，也不会错位。 String desc; String code; public boolean notUsed() { return code == null; } }

It will be easier to find the ones with empty code in the List, but even better, use an unusedList to save all notUsedCoupon.

The second scenario is used as classification statistics. There is a ready-made grouping method in guava. After the grouping is constructed, the number of each group will be known.

In the third scenario, it is not necessary to take an attribute each. In fact, you can construct an object reference to Foo and Bar, and use delegation to
these two objects respectively.

As the respondent mentioned above, there is a lack of high-level design here. When there are three attributes a, b, and c, if you design three Lists respectively, then there will be a search process of
a->b, b->c, and a more complicated operation is a->( b, c). If they are in an object, then a->o(a,b,c) can complete most of the data indexing work.

Python is an interpreted language that can dynamically obtain attributes at runtime

I don’t know Java very well, but there should be several similar reflection mechanisms.

Java is an ancient language. If it is not expressive enough as you said, why has it become the most popular language in the world? It’s just that you didn’t learn it well

Don’t use arrays or lists to separate tickets and codes. There should be a one-to-one relationship between tickets and codes. When building a model, you can create a ticket class with a code attribute in it. Isn’t this very clear?

Java is a verbose language, and the codes written in java are basically quite verbose (before 8).
Java alone is not as elegant as pyhton and other languages in handling basic operations, but it can be compensated for by tool classes and other Groovy.