Question

我有以下代码，我想修改它，以便我可以声明三个与我存储在ArrayList中的对象相同类型的数组（例如类型Integer的数组， Boolean，Double），将ArrayList和每个找到的对象扫描到其兼容阵列。怎么做？

请帮帮我。提前谢谢。

package task2;

import java.io.ObjectInputStream;
import java.util.ArrayList;

public class Task2 {

    public static void main(String[] args) {
        ArrayList<Object> something=new ArrayList<Object>();

        //Array elements for integer type
        something.add(10);
        something.add(20);
        something.add(30);
        something.add(40);
        something.add(50);
        something.add(60);

        ////Array elements for boolean type
        something.add("The color of the sky is blue");
        something.add("The color of tree is green");
        something.add("The color of blood is red");
        something.add("The color of termeric is yello ");
        something.add("The color of dark is black");
        something.add("The color of watar is unknown ");

        ////Array elements for double type
        something.add("-10");
        something.add("-20");
        something.add("-30");
        something.add("-40");
        something.add("-50");
        something.add("-60");
        something.add("-70");
        something.add("-80");


        // Type code to print the integer type object
        System.out.println("Your array is with integer object:");

        for(int intcounter=0; intcounter<5;intcounter++)
        {
            System.out.println(something.get(intcounter));
        }

        // Type code to print the boolean type object
        {

        }

        // Type code to print the boolean type object
        {

        }
    }
}

Answer 1

我认为这就是你想要的：

List integers = new ArrayList<Integer>();
List doubles = new ArrayList<Double>();
List booleans = new ArrayList<Boolean>();

for(Object obj: something){
    if(obj instanceof Integer){
       integers.add(obj)
    }
    else if(obj instanceof Double){
       doubles.add(obj)
    }
    else if(obj instanceof Boolean){
       booleans.add(obj)
    }

}

Answer 2

您可以使用Guava，例如：

Iterable<Integer> onlyIntegers = Iterables.filter(something, Integer.class);

Answer 3

您可以执行以下操作..但您需要稍微改变您的数组输入..因为您这样做的方式，您添加字符串作为布尔和双打，您需要添加实际原始类型。

    if (obj instanceof Integer) {
         System.out.println("Found Integer:" + obj.toString());
    }
    if (obj instanceof Boolean) {
         System.out.println("Found Boolean:" + obj.toString());
    }
    if (obj instanceof Double) {
         System.out.println("Found Double:" + obj.toString());
    }

我从你的例子中做了一个解决方案，希望它有意义。正如您所看到的，为boolean和double添加的类型是实际类型。

package task2;
import java.io.ObjectInputStream;
import java.util.ArrayList;

public class Task2 {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    ArrayList<Object> something=new ArrayList<Object>();

    //Array elements for integer type
    something.add(10);
    something.add(20);
    something.add(30);
    something.add(40);
    something.add(50);
    something.add(60);

    ////Array elements for boolean type
    something.add(true);
    something.add(false);

    ////Array elements for double type
    something.add(40.1);
    something.add(50.1);
    something.add(60.1);
    something.add(70.1);
    something.add(80.1);


    // Type code to print the integer type object
    System.out.println("Your array is with integer object:");

    for(int i=0; i<something.size();i++){
       Object obj = something.get(i);

       if (obj instanceof Integer) {
          System.out.println("Found Integer:" + obj.toString());
       }
       if (obj instanceof Boolean) {
          System.out.println("Found Bool:" + obj.toString());
       }
       if (obj instanceof Double) {
           System.out.println("Found Double:" + obj.toString());
       }
    }
  }
}

如何打印数组的三种不同类型的对象（其中可以存储任何类型的对象）并将其打印在分隔数组中？

3 个答案: