java - 动态创建图形常量

Question

我需要一些帮助来创建常量我使用静态值创建了一个常量，如下所示

private static final Graph.Edge[] GRAPH = {
  new Graph.Edge("a", "b", 7),
  new Graph.Edge("a", "c", 9),
  new Graph.Edge("a", "f", 14),
  new Graph.Edge("b", "c", 10),
  new Graph.Edge("b", "d", 15),
};

图边方法是

public static class Edge {
    public final String v1, v2;
    public final int dist;
    public Edge(String v1, String v2, int dist) {
        this.v1 = v1;
        this.v2 = v2;
        this.dist = dist;
    }
}

当在数组中提供数据时，如何动态创建图形常量？

Answer 1

如果您确定希望 GRAPH 成为常量，您可以这样做:

//do not assign value yet
private static final Graph.Edge[] GRAPH;

...

//static initializer block
static{
  //get a reference to the array you are talking about
  //You can do whatever you like with tempGraph, not necessarily in one line
  Graph.Edge[] tempGraph = {
    new Graph.Edge("a", "b", 7),
    new Graph.Edge("a", "c", 9),
    new Graph.Edge("a", "f", 14),
    new Graph.Edge("b", "c", 10),
    new Graph.Edge("b", "d", 15),
  };
  //you set GRAPH to be the previously built tempGraph 
  //this is what you can do only one time, only in static initalizer block
  GRAPH = tempGraph;
}