如何在Java中动态创建变量？
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How to create variables dynamically in Java?
提问by Andrei Vasilev
I need to create new variables Stringssuch that
我需要创建新的变量Strings，这样
String person1 = "female";
String person2 = "female";
........
........
String person60 = "male";
........
String person100 = "male";
This is what I tried
这是我试过的
for (int i = 1; i <101; i++) {
if (i<60) {
String person+i = "female";
}
else {
String person+i = "male";
}
}
Can anybody help me correct this code?
有人可以帮我更正这段代码吗？
采纳答案by MeBigFatGuy
A Map allows you to relate any key with any value. In this case, the key is the name of the variable, and the value is the value
Map 允许您将任何键与任何值相关联。在这种情况下，键是变量的名称，值是值
Map<String, String> details = new HashMap<>();
for (int i = 1; i <101; i++) {
if (i<60) {
details.put("person" + i, "female");
}
else {
details.put("person" + i, "male");
}
}
回答by Little Child
You will need a String[]of some size that you can determine dynamically.
Then, assign values to the array elements.
您将需要一个String[]可以动态确定的大小。
然后，为数组元素赋值。
String[] anArray;
// some magic logic
anArray = new String[100];
for(int i = 0; i < anArray.length; i++){
// more magic logic to initialize the elements
}
Another option is a Vector<>or ArrayList<>like so:
另一种选择是Vector<>或ArrayList<>像这样：
List<String> anExpandableArray = new ArrayList<String>();
// add String data
anExpandaleArray.add("Foo");
anExpandaleArray.add("Bar");
回答by 06needhamt
Just Use an array like so
只需使用像这样的数组
String[] people = new String[numofelements];
And to initialise the array
并初始化数组
for(int i = 0; i < people.length; i++){
people[i] = "whatever";
}
回答by fvrghl
You are close. If you store the the gender of each person in an array, you can do it like this:
你很近。如果您将每个人的性别存储在一个数组中，您可以这样做：
String[] persons = new String[100]
for (int i = 0; i < persons.length; i++) {
if (i<60) {
persons[i] = "female";
}
else {
persons[i] = "male";
}
}
Alternately, if a person is more than a gender, consider making a class Personthat holds a gender field, and then have an array of Persons. You would set the gender in a similar way.
或者，如果一个人不仅仅是一个性别，可以考虑创建一个Person包含性别字段的类，然后有一个Persons数组。您可以以类似的方式设置性别。
回答by Christian Fries
You might use a Map<String,String>where the key is your "variable name" and the value is the value of that variable.
您可以使用 a Map<String,String>，其中键是您的“变量名”，值是该变量的值。
回答by user278064
String[] persons = new String[101];
for (int i = 0; i < 101; i++) {
if (i < 60) {
String persons[i] = "female";
} else {
String persons[i] = "male";
}
}
回答by T.J. Crowder
When you find yourself wanting to create "more variables" of the same type, you usually want a list of some kind. There are two fundamental kinds of "lists" in Java: Arrays, and Lists.
当您发现自己想要创建相同类型的“更多变量”时，您通常需要某种类型的列表。Java 中有两种基本类型的“列表”：数组和Lists。
An array:
数组：
String[] people = new String[10]; // That gives you room for 10
people[0] = "female";
people[1] = "male";
// ...
int n = 1;
System.out.println("Person " + n + " is " + people[n]);
A List:
答List：
List<String> people = new LinkedList<String>(); // Expandable
people.add("female");
people.add("male");
// ...
int n = 1;
System.out.println("Person " + n + " is " + people.get(n));
// Note difference -------------------------------^^^^^^^
Using an array is great when you know in advance how many there will be. Using a list is great when you don't know how many there will be.
当您提前知道将有多少个数组时，使用数组非常有用。当您不知道将有多少时，使用列表非常有用。
Note on lists: There's an interface, List, and then there are multiple different concrete implementations of it with different runtime performance characteristics (LinkedList, ArrayList, and so on). These are in java.util.
列表注意事项：有一个接口, List，然后有多个不同的具体实现，具有不同的运行时性能特征（LinkedList、ArrayList等）。这些在java.util.
