java - 对象初始化语法 : someVar = (SomeClass[]) Object[aVariable]

Question

在以下来自 https://introcs.cs.princeton.edu/java/44st/BinarySearchST.java.html 的代码片段中keys = (Key[]) new Comparable[initCapacity]; 做什么？

public class BinarySearchST<Key extends Comparable<Key>, Value> {
    private static final int INIT_SIZE = 8;

    private Value[] vals;    // symbol table values
    private Key[] keys;      // symbol table keys
    private int n = 0;       // number of elements

    public BinarySearchST() {
        this(INIT_SIZE);
    }

    public BinarySearchST(int initCapacity) {
        vals = (Value[]) new Object[initCapacity];
        keys = (Key[]) new Comparable[initCapacity];
    } ...

Answer 1

你可以这样分解:

初始化一个new Object大小数组 initCapacity

Object [] someValues = new Object[initCapacity];
Comparable [] someComparable = new Comparable[initCapacity];

然后将数组类型转换为 Value 类型的数组

vals = (Value[]) someValues;
keys = (Keys[]) someComparable;

您上面的语句是在单行上执行这些操作。请记住，您已声明 vals作为 Values 的数组和 keys作为 Keys 的数组.