ex8(4).java

来自「JAVA编程思想第四版英文原版习题答案. pdf原版的」· Java 代码 · 共 24 行

// arrays//Ex8.java
// TIJ4 Chapter Arrays, Exercise 8, page 762
// Demonstrate the assertions in the previous paragraph.

class A {}

public class Ex8<T> {
	@SuppressWarnings("unchecked")
	T[] a = (T[])new Object[2]; // Compile warning: unchecked cast
	public static void main(String[] args) {
		String[] sa = new String[2];
		// sa[0] = new Integer(0); // error: incompatible types
		Object[] oa = new Object[3];
		oa[0] = new String("hi");
		oa[1] = new A(); // arbitrary object OK
		int x = 2;
		oa[2] = x; // Autoboxing converts int to Integer:
		System.out.println("oa[2]: " + oa[2].getClass());
		oa = sa;
		System.out.println("oa: " + oa.getClass());
		// compiles, but Runtime ArrayStoreException:
		// oa[0] = 3;
	}	
}