public class Category {
private Category parentCategory;
private Set<Category> childCategories;
private String name;
public Category() {
childCategories = new HashSet<Category>();
}
public Category getParentCategory() {
return parentCategory;
}
public void setParentCategory(Category parentCategory) {
this.parentCategory = parentCategory;
}
public Set<Category> getChildCategories() {
return childCategories;
}
public void setChildCategories(Set<Category> childCategories) {
this.childCategories = childCategories;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Category [childCategories=" + childCategories + ",name="
+ name + ",parentCategory=" + parentCategory + "]";
}
}
public static void main(String[] args) {
Category books = new Category();
books.setName("Books");
books.setParentCategory(null);
Category novels = new Category();
novels.setName("Novels");
novels.setParentCategory(books);
books.getChildCategories().add(novels);
//novels.setChildCategories(null);
System.out.println("Books > " + books);
}
System.out.println正在生成StackOverflowError.
解决方法
当你做toString()时,你调用toString()的孩子.这里没有问题,除了你在这里调用父节点的toString().这将调用toString()的孩子等
很好的无限循环.
@Override
public String toString() {
return "Category [childCategories=" + childCategories + ",name="
+ name + ",parentCategory=" + parentCategory.getName() + "]";
}
这样你不要打印parentCategory,而只打印它的名字,没有无限循环,没有StackOverflowError.
编辑：正如Bolo在下面所说的,你需要检查parentCategory不是null,如果是,那么你可能有一个NullPointerException.
资源：
> Javadoc – StackOverflowError
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> toString() in java
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