public class Book {
String title;
String author;
class BooksTestDrive {
}
public static void main(String [] args) {
Book [] myBooks = new Book[3];
int x = 0;
myBooks[0].title = "The Grapes of Java";
myBooks[1].title = "The Java Gatsby";
myBooks[2].title = "The Java Cookbook";
myBooks[0].author = "bob";
myBooks[1].author = "sue";
myBooks[2].author = "ian";
while (x < 3) {
System.out.print(myBooks[x].title);
System.out.print( "by" );
System.out.println(myBooks[x].author);
x = x + 1;
}
}
}为什么没有提示错误，运行的时候却有问题呢？
对数组的初始化工作没有结束，在Java中对非基本数据初始化时，必须使用new。在使用new创建数组后，此时数组还是一个引用数组。只有再创建新的对象，并把对象赋值给数组引用，到此初始化结束。
public class Book {
String title;
String author;
public static void main(String [] args) {
Book[] myBooks = new Book[3];
myBooks[0] = new Book();
myBooks[1] = new Book();
myBooks[2] =new Book();
myBooks[0].title = "The Grapes of Java";
myBooks[1].title = "The Java Gatsby";
myBooks[2].title = "The Java Cookbook";
myBooks[0].author = "bob";
myBooks[1].author = "sue";
myBooks[2].author = "ian";
for(int x = 0; x < 3; x++ ){
System.out.print(myBooks[x].title);
System.out.print( " by " );
System.out.println(myBooks[x].author);
}
}
}