java如何打印HashMap值？输出像xxx@da52a1

Question

我有两门课

梅因。爪哇

import java.util.HashMap;
import java.util.Map;

public class Main {
    Map<Integer, Row> rows = new HashMap<Integer, Row>();
    private Row col;

    public Main() {
        col = new Row();
        show();
    }

    public void show() {
        // col.setCol("one", "two", "three");
        // System.out.println(col.getCol());

        Row p = new Row("raz", "dwa", "trzy");
        Row pos = rows.put(1, p);
        System.out.println(rows.get(1));

    }

    public String toString() {
        return "AA: " + rows;
    }

    public static void main(String[] args) {
        new Main();
    }
}

还有划船。爪哇

public class Row {

    private String col1;
    private String col2;
    private String col3;

    public Row() {
        col1 = "";
        col2 = "";
        col3 = "";
    }

    public Row(String col1, String col2, String col3) {
        this.col1 = col1;
        this.col2 = col2;
        this.col3 = col3;
    }

    public void setCol(String col1, String col2, String col3) {
        this.col1 = col1;
        this.col2 = col2;
        this.col3 = col3;
    }

    public String getCol() {
        return col1 + " " + col2 + " " + col3;
    }
}

输出总是看起来像“Row@da52a1“或类似的。如何解决这个问题？我希望能够轻松访问每个字符串：

str="string1","string2","string3"; // it's kind of pseudocode ;)
rows.put(1,str);
rows.get(1);

如您所见，我创建了类行以将其用作Map的对象，但我不知道我的代码出了什么问题

Answer 1

向Row类添加一个自定义toString方法toString是每个Java对象都拥有的方法。在这种情况下它是存在的

Answer 2

你越来越坚强了Row@da52a1，因为您最终调用了字符串的默认toString方法，该方法以十六进制表示法将对象的类名与哈希代码结合起来

通过创建自己的toString方法，可以告诉编译器在对对象调用toString时要显示哪些值

@Override
public String toString() {
    return this.col1 + " " + this.col2 + " " + this.col3;
}