Question

这个方法给了我一个空指针异常，我不知道为什么会这样。递归代码有问题。我想不出来。

 public void clearAllSelections(){
    //Recursively clear all the selections in the sub-tree of this node
    //basis:
    isSelected = false;
    if(isLeaf()) return;

    //recursion:
    childrenRight.clearAllSelections();
    childrenLeft.clearAllSelections();

}

Answer 1

您的isLeaf()检查是不够的，因为二叉树中的节点可能只有一个子节点，因此您必须添加空检查：

public void clearAllSelections(){
    //Recursively clear all the selections in the sub-tree of this node
    //basis:
    isSelected = false;
    if(isLeaf()) return;

    //recursion:
    if (childrenRight != null)
        childrenRight.clearAllSelections();
    if (childrenLeft != null)
        childrenLeft.clearAllSelections();

}

Answer 2

在进行函数调用之前对childrenRight和childrenLeft进行空检查

重复二叉树方法上的Java空指针异常

2 个答案: