访问类数组字段

时间:2013-02-01 14:50:18

标签: java arrays get field

我在for循环中从数组访问字段时遇到问题。我确定我只是弄乱了语法:

public class Person {

String  name;
Person  mother;
Person  father;
ArrayList<Person> children;

public boolean isMotherOf(Person pers1) {
    //First check if Persons mother equals pers1
    if (mother.name == pers1.name) {            
        //Second checks if pers1s children contains Person
        for (int i = 0; i < pers1.children.size(); i++) {
            if (pers1.children.name.get(i) == name) {
// ERROR ON THE LINE ABOVE: "name cannot be resolved or it not a field"
                return true;
            } 
        } // END second check
    } else { return false; }


    } // END method isMotherOf
}

编辑:我的代码包含逻辑错误(比较错误的人)。这个安全检查是否有效,或者当检查pers1的母亲是否有名字时,如果pers1不存在会产生错误吗?

public class Person {

String  name;
Person  mother;
Person  father;
ArrayList<Person> children;

// Checks if THIS person is the mother of pers1
public boolean isMotherOf(Person pers1) {
    // Safety check: Both persons exists and Person has children and pers1 has mother 
    if (name == null || children == null || pers1 == null
        || pers1.mother.name == null) {
        return false;
    } // END safety check
    // First check if Persons name equals pers1's mother
    else if (name.equals(pers1.mother.name)) {          
        // Second check if Persons children contains pers1
        for (int i = 0; i < children.size(); i++) {
            if (children.get(i).name.equals(pers1.name)) {
                return true;
            } 
        } // END second check
    } // END first check 
    return false;
} // END method isMotherOf
} // END class Person

3 个答案:

答案 0 :(得分:4)

您交换了两件事,pers1.children.name.get(i)应为pers1.children.get(i).name

由于我们在这里,您正在将字符串与==进行比较,这比较了对象的引用,而是使用equals(..)。请查看here

答案 1 :(得分:0)

您似乎正在使用==代替equals()函数来比较字符串。

尝试按以下方式更改此行:

if (pers1.children.name.get(i).equals(name))

答案 2 :(得分:0)

不要使用“==”进行字符串比较;这不符合你的想法。你想把它写成:

if (mother.name.equals(pers1.name)) { ...

当然,这是一种稍微危险的方法,因为如果NullPointerExceptionmother为空,您将获得mother.name。所以你会想做一些防御性的编程。

if (mother == null) return false;
if (pers1 == null) return false;
if (mother.name != null && mother.name.equals(pers1.name)) ....