[英]How to return unique values in a list without reordering
In the following code, I have an arraylist that contains duplicated values: 在下面的代码中,我有一个包含重复值的arraylist:
List<Double> fitnesses = new ArrayList<Double>();
fitnesses.add(5.0);
fitnesses.add(1.0);
fitnesses.add(5.0);
fitnesses.add(2.0);
fitnesses.add(4.0);
fitnesses.add(2.0);
I want to remove the duplicates and for that I used the following: 我想删除重复项,为此我使用了以下内容:
Set<Double> hashsetList = new HashSet<Double>(fitnesses);
The problem is that the output that I get is: 问题是我得到的输出是:
[1.0, 2.0, 4.0, 5.0]
The issue is that I don't want the values to be sorted. 问题是我不希望对值进行排序。 Is there any way to remove the duplicates without reordering
有没有办法删除重复项而不重新排序
You can use stream with distinct property. 您可以使用具有不同属性的流。
distinct()
is a function of stream which is added in java 8 distinct()
是在java 8中添加的流的函数
NOTE: If using java8 注意:如果使用java8
List<Double> distinctList = fitnesses.stream().distinct().collect(Collectors.toList());
NOTE: Before JAVA8 注意:在JAVA8之前
Set<Double> uniqueRecords = new LinkedHashSet<Double>();
for (Double value : fitnesses){
uniqueRecords.add(value);
}
System.out.println(uniqueRecords);
Or we van use: 或者我们使用:
Set<Double> uniqueRecords = new LinkedHashSet<Double>(fitnesses);
Output = [5.0, 1.0, 2.0, 4.0] 输出= [5.0,1.0,2.0,4.0]
如果您不想/不能使用java 8方法,可以将值插入到LinkedHashSet
,它会保留插入顺序。
You can achieve this with java 8 stream and distinct
command: 您可以使用java 8 stream和
distinct
命令实现此目的:
List<Double> collect = fitnesses.stream()
.distinct() //this is where the magic happens
.collect(Collectors.toList());
Output: 输出:
[5.0, 1.0, 2.0, 4.0]
[5.0,1.0,2.0,4.0]
In J8 as the other answer this is the most effiscient : 在J8作为另一个答案,这是最有效的:
List<Double> collect = fitnesses.stream()
.distinct()
.collect(Collectors.toList());
You can also use a java.util.LinkedHashSet if you are not Java 8 如果您不是Java 8,也可以使用java.util.LinkedHashSet
Set<Double> hashsetList = new LinkedHashSet<Double>(fitnesses);
LinkedHashSet will preserve the order of added elements LinkedHashSet将保留添加元素的顺序
Using LinkedHashSet
seems to work: 使用
LinkedHashSet
似乎工作:
public void test() throws InterruptedException {
List<Double> fitnesses = new ArrayList<Double>();
fitnesses.add(5.0);
fitnesses.add(1.0);
fitnesses.add(5.0);
fitnesses.add(2.0);
fitnesses.add(4.0);
fitnesses.add(2.0);
System.out.println("Original: "+fitnesses);
// Get the unduplicated set.
Set<Double> hashsetList = new LinkedHashSet<>(fitnesses);
System.out.println("Deduplicated: "+hashsetList);
}
Original: [5.0, 1.0, 5.0, 2.0, 4.0, 2.0]
原文:[5.0,1.0,5.0,2.0,4.0,2.0]
Unduplicated: [5.0, 1.0, 2.0, 4.0]
无重复:[5.0,1.0,2.0,4.0]
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