I want my String[] array; to be static but I still don't know it's size.
我想要我的String []数组;是静态但我仍然不知道它的大小。
Is there any way to declare string array of unknown size? As much as possible I don't want to use ArrayList
有没有办法声明未知大小的字符串数组？我尽可能不想使用ArrayList
6 个解决方案
#1
15
You don't need to know the array size when you declare it
声明它时，您不需要知道数组大小
String[] myArray;
but you do need to know the size when you initialize it (because Java Virtual Machine needs to reserve a continuous chunk of memory for an array upfront):
但是在初始化时需要知道大小（因为Java虚拟机需要预先为阵列预留一块连续的内存）：
myArray = new String[256];
If you don't know what the size will need to be in the moment you initialize it, you need a List<String>, or you'll be forced to make your own implementation of it (which is almost certainly worse option).
如果你不知道在初始化它时需要的大小，你需要一个List
#2
3
String [] array = new String[1];
it will be garbage collected later after you init with a real array n elements.
在使用真正的数组n个元素初始化之后，它将被垃圾收集。
array = new String[n];
ofcourse it has a performance decrease but it should be non-importance unless you repeat same for many different arrays.
当然，它有性能下降但它应该是不重要的，除非你对许多不同的数组重复相同。
#3
2
No, it needs to be declared, and thus have a length before you can set elements in it.
不，它需要声明，因此在你可以设置元素之前有一个长度。
If you want to resize an array, you'll have to do something like: Expanding an Array?
如果要调整数组大小，则必须执行以下操作：扩展数组？
#4
1
The list is better for manipulation of an "array" for which you don't know length.
该列表更适合操作您不知道长度的“数组”。
#5
1
Using Java.util.ArrayList or LinkedList is the usual way of doing this. With arrays that's not possible as I know.
使用Java.util.ArrayList或LinkedList是执行此操作的常用方法。对于我不知道的阵列。
Example:
例：
List unindexedVectors = new ArrayList();
列表unindexedVectors = new ArrayList（）;
unindexedVectors.add(2.22f);
unindexedVectors.add（2.22f）;
unindexedVectors.get(2);
unindexedVectors.get（2）;
#6
0
My apologies to the nay-say-ers, this can be done easily.
我向那些说不出口的人道歉，这很容易做到。
import java.util.Random;
public class Roll_2 {
static Random random = new Random();
public static void main(String[] args) {
int[] variableArray1 = init(random.nextInt(9)); // random size
int[] variableArray2 = init(random.nextInt(9)); // random size
int[] variableArray3 = init(random.nextInt(9)); // random size
randomaize(variableArray1); // randomize elements
randomaize(variableArray2); // randomize elements
randomaize(variableArray3); // randomize elements
print(variableArray1); // print final
print(variableArray2); // print final
print(variableArray3); // print final
}
private static int[] init(int x) {
int[] arr = new int[x];
return arr;
}
private static void print(int[] body) {
System.out.print("[");
for (int i=0;i<body.length;i++) {
System.out.print(body[i]);
if (i<body.length-1) System.out.print(" ");
}
System.out.println("]");
}
private static void randomaize(int[] body) {
for (int i=0;i<body.length;i++) {
body[i] = random.nextInt(9);
}
}
}
Sample Run 1: [1 7 2] [5 2 8 6 8 3 0 8] []
样本运行1：[1 7 2] [5 2 8 6 8 3 0 8] []
Sample Run 2: [2 5 6 8 0 7 0 6] [0 0 1] [2 1 2 1 6]
样本运行2：[2 5 6 8 0 7 0 6] [0 0 1] [2 1 2 1 6]
Sample Run 3: [8 3 3] [7] [1 3 7 3 1 2]
样本运行3：[8 3 3] [7] [1 3 7 3 1 2]
#1
15
You don't need to know the array size when you declare it
声明它时，您不需要知道数组大小
String[] myArray;
but you do need to know the size when you initialize it (because Java Virtual Machine needs to reserve a continuous chunk of memory for an array upfront):
但是在初始化时需要知道大小（因为Java虚拟机需要预先为阵列预留一块连续的内存）：
myArray = new String[256];
If you don't know what the size will need to be in the moment you initialize it, you need a List<String>, or you'll be forced to make your own implementation of it (which is almost certainly worse option).
如果你不知道在初始化它时需要的大小，你需要一个List
#2
3
String [] array = new String[1];
it will be garbage collected later after you init with a real array n elements.
在使用真正的数组n个元素初始化之后，它将被垃圾收集。
array = new String[n];
ofcourse it has a performance decrease but it should be non-importance unless you repeat same for many different arrays.
当然，它有性能下降但它应该是不重要的，除非你对许多不同的数组重复相同。
#3
2
No, it needs to be declared, and thus have a length before you can set elements in it.
不，它需要声明，因此在你可以设置元素之前有一个长度。
If you want to resize an array, you'll have to do something like: Expanding an Array?
如果要调整数组大小，则必须执行以下操作：扩展数组？
#4
1
The list is better for manipulation of an "array" for which you don't know length.
该列表更适合操作您不知道长度的“数组”。
#5
1
Using Java.util.ArrayList or LinkedList is the usual way of doing this. With arrays that's not possible as I know.
使用Java.util.ArrayList或LinkedList是执行此操作的常用方法。对于我不知道的阵列。
Example:
例：
List unindexedVectors = new ArrayList();
列表unindexedVectors = new ArrayList（）;
unindexedVectors.add(2.22f);
unindexedVectors.add（2.22f）;
unindexedVectors.get(2);
unindexedVectors.get（2）;
#6
0
My apologies to the nay-say-ers, this can be done easily.
我向那些说不出口的人道歉，这很容易做到。
import java.util.Random;
public class Roll_2 {
static Random random = new Random();
public static void main(String[] args) {
int[] variableArray1 = init(random.nextInt(9)); // random size
int[] variableArray2 = init(random.nextInt(9)); // random size
int[] variableArray3 = init(random.nextInt(9)); // random size
randomaize(variableArray1); // randomize elements
randomaize(variableArray2); // randomize elements
randomaize(variableArray3); // randomize elements
print(variableArray1); // print final
print(variableArray2); // print final
print(variableArray3); // print final
}
private static int[] init(int x) {
int[] arr = new int[x];
return arr;
}
private static void print(int[] body) {
System.out.print("[");
for (int i=0;i<body.length;i++) {
System.out.print(body[i]);
if (i<body.length-1) System.out.print(" ");
}
System.out.println("]");
}
private static void randomaize(int[] body) {
for (int i=0;i<body.length;i++) {
body[i] = random.nextInt(9);
}
}
}
Sample Run 1: [1 7 2] [5 2 8 6 8 3 0 8] []
样本运行1：[1 7 2] [5 2 8 6 8 3 0 8] []
Sample Run 2: [2 5 6 8 0 7 0 6] [0 0 1] [2 1 2 1 6]
样本运行2：[2 5 6 8 0 7 0 6] [0 0 1] [2 1 2 1 6]
Sample Run 3: [8 3 3] [7] [1 3 7 3 1 2]
样本运行3：[8 3 3] [7] [1 3 7 3 1 2]