函数建议的 Var 列表

Question

我做了一个简单的程序来反转列表。现在我试图反转一个字符串，所以我将它转换成一个字符数组并将它分配给一个变量 charz.But 我的函数只接受一个字符串列表。

现在在 python 中，我可以有多个变量类型的列表，例如 a = [1,"hello",1.3] 如果有相同的方法，这不会有问题这样的列表，以便我可以在我的函数中使用它？我如何让它接受这个变量 charz 而不只为这个特定的数据类型创建一个新函数。

package test_proj1;

import java.util.Arrays;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

class TestClass1
{
    static Scanner reader = new Scanner(System.in);

    public static void main (String[] args)
    {
        List<String> sent = new ArrayList<String>(Arrays.asList("Jake","you","are"));
        System.out.println("Without reversal the inuilt list is "+sent);
        sent = lisrev(sent);
        System.out.println("After reversal the list is "+ sent);
        System.out.println("\nNow then enter a word for me: ");
        String word = reader.nextLine();
        char[] charz = word.toCharArray();
        // List<String> revword = lisrev(charz);  
        // I want the above line to work but it won't because my function
        // lisrev will only accept  a list of type String




    }
    public static List<String> lisrev (List<String> lis)
    {
        int lastindex = lis.size() - 1;
        List<String> newlis = new ArrayList<String>();


        while (lastindex != -1)
        {
            String elem = lis.get(lastindex);
            newlis.add(elem);
            lastindex -= 1;
        }


        return newlis;
    }

}

Answer 1

char[] charz = word.toCharArray();
String wordReversed = "";
for (int i=charz.length-1; i>=0; i--){
      wordReversed+= charz[i];
}
System.out.println(wordReversed);

结果将是例如：

Without reversal the inuilt list is [Jake, you, are]
After reversal the list is [are, you, Jake]

Now then enter a word for me: 
Hello My name is Sam, How are you today?
?yadot uoy era woH ,maS si eman yM olleH

此外，如果你想反转用户的句子，你可以这样做：

List<String> theWord = new ArrayList<String>();
String eachWord="";
for(int i=0; i<charz.length; i++){
    eachWord+=charz[i]; // append the char to the String
    if(charz[i]==' ' || i==charz.length-1){
       if(!eachWord.replace(" ", "").equals("")){ // for the followed spaces
          theWord.add(eachWord.replace(" ", "")); // add the word 
       }
       eachWord = ""; // start new string
    }
}
System.out.println(lisrev(theWord));

结果将是例如（注意空格）

Without reversal the inuilt list is [Jake, you, are]
After reversal the list is [are, you, Jake]
Now then enter a word for me: 
Hello My name is Sam,   How are   you today 
[?, today, you, are, How, Sam,, is, name, My, Hello]

Answer 2

如果您希望您的列表包含多种不同的数据类型，请将您的列表声明为 Object，例如：

List<Object> sent = new ArrayList<Object>(Arrays.asList("Jake","you","are", 20, "years", "old", "and", 70.3, "inches", "high"));
for (int i = 0; i < sent.size(); i++) {
    System.out.println(sent.get(i).toString());
}

但是，如果您想将列表的元素分解为特定的数据类型变量，如 String、int、double 等，那么您需要对其进行强制转换，例如：

String name = (String) sent.get(0); //or use: sent.get(0).toString();
int age = (int) sent.get(3);
double height = (double) sent.get(7);

如果您希望列表中的双精度或整数类型为字符串，您可以执行以下任一操作：

对于整数、双精度、浮点数等：

String age = sent.get(3).toString();

或

String age = String.valueOf(sent.get(3));

函数建议的 Var 列表

Var List for function suggestion

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