Question

我正在尝试构建一个自定义对象引用数组。这是一些简化的代码。

import java.util.*;

public class Map {

    private int[] dimension;

    private City[] cities;
    private int nCities;

    public static void main( String[] args ) {
        Map map = new Map( 5, 20, 500, 500 );
    }

    public Map( int nCities, int diameter, int w, int h ) {
        this.dimension = new int[2];

        this.dimension[0] = w;
        this.dimension[1] = h;

        this.create_cities( nCities, diameter );
    }

    private void create_cities( int nCities, int diameter ) {
        // data
        this.cities = new City[nCities];
        this.nCities = nCities;

        // locate cities
        long seed = System.currentTimeMillis();
        Random random = new Random( seed );

        int[] location = new int[2];

        for( int n = 0; n < nCities; n++ ) {
            location[0] = random.nextInt( this.dimension[0] );
            location[1] = random.nextInt( this.dimension[1] );

            this.cities[n] = new City( diameter, location );

            System.out.println( this.cities[n].toString() );
        }
        System.out.println( "\n" + Arrays.toString( this.cities ) );
    }
}

结果：

diameter: 20, location: [311, 324]
diameter: 20, location: [85, 294]
diameter: 20, location: [364, 182]
diameter: 20, location: [269, 412]
diameter: 20, location: [123, 200]

[diameter: 20, location: [123, 200], diameter: 20, location: [123, 200], diameter: 20, location: [123, 200], diameter: 20, location: [123, 200], diameter: 20, location: [123, 200]]

有人能从墙上拔掉我的头吗？我存储相同的参考5次，对吗？我怎么不这样做？我想存储对每个唯一City对象的引用。

Answer 1

您在每个城市存储相同的location数组。为每个人制作一个新阵列，你应该很高兴。

    for( int n = 0; n < nCities; n++ ) {
        int[] location = new int[2];
        location[0] = random.nextInt( this.dimension[0] );

Answer 2

        this.cities[n] = new City( diameter, location );

这是将同一个“位置”对象的参考分配给每个城市，因此最后当您打印所有城市时，它会将位置显示为最新的对象参考。

移动

       int[] location = new int[2];

循环内的

     for( int n = 0; n < nCities; n++ ) {

或只是

        this.cities[n] = new City( diameter, new int[](random.nextInt( this.dimension[0] ),random.nextInt( this.dimension[1] ) );

Answer 3

在创建City对象时，您将相同的直径和位置传递给City构造函数，每次创建City对象时都需要找到一种方法来传递不同的直径和位置。

将不同的直径和位置存储在数组中，并在创建City Object时传递正确的值。

Java：自定义对象引用的数组

3 个答案: