我已将这些树及其相关数据放入名为trees的ArrayList中。然后我让系统打印出他们的ID和相关的适用性值。代码如下。
最后,我想要打印出最高的适用性值,但我一直在最大限度地说错误:
“绑定不匹配:通用方法
max(Collection<? extends T>)
类型Collections
不适用于参数 (ArrayList<Trees>
)。推断类型Trees不是有效的替代品 对于有界参数<T extends Object & Comparable<? super T>>
“
我似乎无法弄清楚这意味着什么。如果您需要查看更多代码,请与我们联系。
有谁知道我如何获得最高的适用性值(最接近1的值)?
int treeCount = 10;
for (int i = 0; i < treeCount; i++) {
double suitability = RandomHelper.nextDoubleFromTo(0, 1);
int id = i;
context.add(new Trees(space, grid, suitability, id));
ArrayList<Trees> trees = new ArrayList<Trees>();
Trees tree;
tree = new Trees(space, grid, suitability, id);
trees.add(tree);
System.out.println("Tree " + id + " has a suitability of " + suitability);
Object obj = Collections.max(trees);
System.out.println(obj);
}
答案 0 :(得分:4)
您可能忘记实施Comparable<T>
..如果不这样做,就无法确定哪棵树是“最大的”..
您可能希望这样做:
public class Tree implements Comparable<Tree> {
@Override
public int compareTo(Tree o) {
// use the value which should be used for comparison instead of getSuitability().
// remember: here you have private access to object o. if your value is not a
// double, there is also a Integer.compare(..) function, but you could also just
// return value - other.value..
return Double.compare(getSuitability(), o.getSuitability());
}
// .. code ..
}
如果您无法修改Tree
课程,则可以随时实施Comparator<Tree>
public class TreeComparator implements Comparator<Tree> {
@Override
public int compare(Tree o1, Tree o2) {
return Double.compare(o1.getSuitability(), o2.getSuitability());
}
}
并将其与Collections.max(Collection, Comparator)
函数一起使用:
Tree maxTree = Collections.max(trees, new TreeComparator());
如果您经常调用此代码,请考虑将new TreeComparator()
调用解析为常量。
答案 1 :(得分:1)
看起来Trees
无法比较。
思考 - Collections.max(trees)
如何确定最大树是什么?
您有两种选择:
Trees
实施Comparable
实施Comparator
并致电Collections.max(trees, comparator)