二元运算符的错误操作数类型“>”？ [英] Bad Operand Types for Binary Operator ">"?

问题描述

我正在写一个BST计划。我收到错误：

I am writing a BST Program. I get the error:

二元运算符的错误操作数类型>

"Bad Operand Types for Binary Operator ">"

第一种类型：java。 lang.Object

first type: java.lang.Object

第二种类型：java.lang.Object

second type: java.lang.Object"

这是它给我的方法错误：

This is the method where it gives me the error:

public void placeNodeInTree(TreeNode current, TreeNode t)                                                                    
{   
    if(current == null)
        current = t;
    else{
       if(current.getValue() > t.getValue()) 
            current.setRight(t);
       if(current.getValue() < t.getValue()) 
            current.setLeft(t);  
        }
}

getValue（）的返回类型为Object，因此java.lang.Object类型。这是我第一次见到这个错误。谁能给我一些关于这个错误的背景知识？谢谢

getValue() has a return type of Object, thus the java.lang.Object types. This is the first time I have ever seen this error. Can anyone give me some background on this error? Thanks

推荐答案

当然 - 您根本无法应用> 对象之间的运算符你期望它做什么？您不能应用任何其他二元运算符 - + ， - ， / etc（字符串连接除外）。

Sure - you simply can't apply the > operator between objects. What would you expect it to do? You can't apply any of the other binary operators either - +, -, / etc (with the exception of string concatenation).

理想情况下，你应该使你的 TreeNode 泛型，并且要么有一个 Comparator< T> ，它能够比较任何两个实例，或者生成 T extend Comparable< T> 。无论哪种方式，您都可以将它们与以下内容进行比较：

Ideally, you should make your TreeNode generic, and either have a Comparator<T> which is able to compare any two instances, or make T extend Comparable<T>. Either way, you can then compare them with:

int comparisonResult = comparator.compare(current.getValue(), t.getValue());
if (comparisonResult > 0) {
  // current "greater than" t
} else if (comparisonResult < 0) {
  // current "less than" t
} else {
  // Equal
}

或

int comparisonResult = current.getValue().compareTo(t.getValue());
// Code as before

如果没有泛型，你可以强制转换值为可比较或仍然使用一般比较器 ...但是泛型将是一个更好的选择。

Without generics you could cast the values to Comparable or still use a general Comparator... but generics would be a better bet.

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