Question

我相信我的Collections.max函数正在返回哈希码，但说实话，我并不完全确定发生了什么。

我正在创建一个具有随机适用性值的树列表，实现比较器，然后尝试找到最高适用性值（代码如下）。

public class Tree {
    public double suitability = Math.random();
    public int id;
    public static int count = 1;

    public Tree(double suitability, int id) {
        this.id = count;
        count++;    
    }

    public double getSuit() {
        return suitability;
    }

    public void setSuit(double suitability) {
        this.suitability = suitability;
    }

    public void measureSuit() {
           System.out.println("Tree number " + id + " has a suitability of " + suitability);
    }

}

class SuitComp implements Comparator<Tree> {

    @Override
    public int compare(Tree o1, Tree o2) {
        return Double.compare(o1.getSuit(), o2.getSuit());
    }   
} 


public class EmeraldRunner {

    public static void main(String[] args) {

        ArrayList<Tree> trees = new ArrayList<Tree>();

        Tree tree;

        int treeCount = 10;
        for (int i = 0; i < treeCount; i++) {
        tree = new Tree(i, i);

        trees.add(tree)

        Tree maxTree = Collections.max(trees, new SuitComp());

        System.out.println(maxTree);
        tree.measureSuit();

        }

    }

}

我的输出如下：

learnFromCave.Tree@60f32dde

第1号树的适用性为0.6114866528786418

learnFromCave.Tree@60f32dde

第2号树的适用性为0.28381422309266247

learnFromCave.Tree@3312b1dd

第3号树的适用性为0.8441348268153896

learnFromCave.Tree@3312b1dd

第4号树的适用性为0.6269071898386682

learnFromCave.Tree@3312b1dd

第5号树的适用性为0.08717540188464434

learnFromCave.Tree@3312b1dd

第6号树的适用性为0.3810530158434646

learnFromCave.Tree@3312b1dd

第7号树的适用性为0.0938353693923476

learnFromCave.Tree@3312b1dd

第8号树的适用性为0.3656868216321937

learnFromCave.Tree@105b3e5d

第9号树的适用性为0.9717207037612301

learnFromCave.Tree@105b3e5d

第10号树的适用性为0.44423960773823645

Answer 1

System.out.println(maxTree);在toString()上致电maxTree。由于你没有覆盖它，它会调用Object上的方法，它只输出完整的类名和一些附加信息。

您需要自己实现toString()以获得更易读的输出。

public class Tree {
    public double suitability = Math.random();
    public int id;
    public static int count = 1;

    public Tree(double suitability, int id) {
        this.id = count;
        count++;
    }

    public double getSuit() {
        return suitability;
    }

    public void setSuit(double suitability) {
        this.suitability = suitability;
    }

    public void measureSuit() {
        System.out.println("Tree number " + id + " has a suitability of " + suitability);
    }

    @Override
    public String toString() {
        return "I am the tree with id " + id;
    }
}

Collections.max函数返回哈希码（我认为）

1 个答案: