要打印对象的内容？

Question

我应该在我的代码中执行哪些更改，以便它可以打印整个家族都尝试过的字符串，我只得到null。这只是一个非常简单的代码soo plss帮助。

    import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

/**
 * Created by Alpit on 26-05-2017.
 */
public class Fam {
    String father;
    String mother;
    String sister;
    String brother;
String r;

    public Fam(String father, String sister, String brother, String mother) {
        this.father = father;
        this.sister = sister;
        this.brother = brother;
        this.mother = mother;
    }

    public String getFather() {
        return father;
    }

    public void setFather(String father) {
        this.father = father;
    }


}
class add {
    public static void main(String args[]) throws IOException {
        BufferedReader obj = new BufferedReader(new InputStreamReader(System.in));
        ArrayList<Object> arrayList = new ArrayList<>();
        for (int i = 0; i < 2; i++) {
            String f = obj.readLine();
            String s = obj.readLine();
            String b = obj.readLine();
            String m = obj.readLine();
            Fam fam = new Fam(f, s, b, m);
            arrayList.add(fam);
        }
        for (Object x : arrayList) {

            System.out.println(String.valueOf(x));

        }
    }
}

我只得到了对象的地址，这个问题可以被认为是这个问题的重复，但我无法理解这里提供的解决方案。

这是我再次尝试的

    import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

/**
 * Created by Alpit on 26-05-2017.
 */
public class Fam {
    String father;
    String mother;
    String sister;
    String brother;
String r;

    public Fam(String father, String sister, String brother, String mother) {
        this.father = father;
        this.sister = sister;
        this.brother = brother;
        this.mother = mother;
    }

    public String getFather() {
        return father;
    }

    public void setFather(String father) {
        this.father = father;
    }

    public String toString()
    {
        return r;
    }


}
class add {
    public static void main(String args[]) throws IOException {
        BufferedReader obj = new BufferedReader(new InputStreamReader(System.in));
        ArrayList<Object> arrayList = new ArrayList<>();
        for (int i = 0; i < 2; i++) {
            String f = obj.readLine();
            String s = obj.readLine();
            String b = obj.readLine();
            String m = obj.readLine();
            Fam fam = new Fam(f, s, b, m);
            arrayList.add(fam);
        }
        for (Object x : arrayList) {

            System.out.println(x.toString());

        }
    }
}

这将返回null。

Answer 1

实现您自己的toString（）方法。这样做：

class Fam {
    String father;
    String mother;
    String sister;
    String brother;
    String r;

    public Fam(String father, String sister, String brother, String mother) {
        this.father = father;
        this.sister = sister;
        this.brother = brother;
        this.mother = mother;
    }

    public String getFather() {
        return father;
    }

    public void setFather(String father) {
        this.father = father;
    }

    public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append(this.father);
        builder.append(" ");
        builder.append(this.sister);
        builder.append(" ");
        builder.append(this.brother);
        builder.append(" ");
        builder.append(this.mother);

        return builder.toString();
    }


} 

class add {
    public static void main(String args[]) throws IOException {
        Fam family = new Fam("father", "sister", "brother", "mother");

        System.out.println(family.toString());
    }
}

我已经在这里实现了toString（）。我使用了StringBuilder来演示如何创建自己的方法，在“父亲、姐妹、兄弟、母亲”之间插入空格。

跑步你得到：

father sister brother mother

Answer 2

什么弦。valueOf（object）的作用是调用类对象的toString（）方法（在您的例子中是Fam）。

 public static String valueOf(Object obj) {
    return (obj == null) ? "null" : obj.toString();

}

因此，您需要在Fam类中重写toString（）方法，如下所示：

public class Fam {
String father;
String mother;
String sister;
String brother;
String r;
public Fam(String father, String sister, String brother, String mother) {
    this.father = father;
    this.sister = sister;
    this.brother = brother;
    this.mother = mother;
}

.
.
.

@Override
public String toString() {
    return this.father +" "+this.mother +" "+ this.sister +" "+ this.brother;
}

此外，您需要在main方法中进行此更改。

        ArrayList<Fam> arrayList = new ArrayList<Fam>();

这样你就可以把你的物品打印出来。（请注意：您可以在toString（）方法中更改返回格式。）

Answer 3

您可以从类Fam中的对象重写toString（）。