重写toString方法

重写toString方法
当需要将一个对象输出到显示器时,通常要调用他的toString()方法,将对象的内容转换为字符串.java中的所有类默认都有一个toString()方法

默认情况下 System.out.println(对象名)或者System.out.println(对象名.toString())输出的是此对象的类名和此对象对应内存的首地址如果想自定义输出信息必须重写toString()方法

注意事项

1.必须被声明为public

2.返回类型为String

3.方法的名称必须为toString,且无参数

4.方法体中不要使用输出方法System.out.println()

例:

package org.tiling.scheduling.examples;

class Patient {
private String name;
private char sex;
private int age;
private float weight;
private boolean allergies;
private int id;
private static int count = 0; // static，用于统计人数

public void print()
// 输出信息 要写void
{
System.out.println("姓名：" + name);// 相当于
System.out.println("序号：" + id);
System.out.println("性别：" + sex);
System.out.println("年龄：" + age);
System.out.println("体重：" + weight);
System.out.println("是否住过院：" + allergies);
System.out.println("当前病人数：" + count);
System.out.println("====================我是分隔线========================");
}

public Patient(String name, char sex, int age, float weight,
boolean allergies) {
= name;
this.sex = sex;
this.age = age;
this.weight = weight;
this.allergies = allergies;
count++;
id = count;
}

public int getId() {
return id;
}

public void setName(String name) {
= name;
}

public String toString() {
java.text.DecimalFormat df = new java.text.DecimalFormat("$0.00"); // $可以不加
return ("姓名：" + name + "\n序号：" + id + "\n性别：" + sex + "\n年龄：" + age
+ "\n体重：" + df.format(weight) + "\n是否住过院：" + allergies
+ "\n人数：" + count + "\n=====================我是分隔线=======================");
}
}

public class PatientTester {
public static void main(String args[]) {
Patient PatientA = new Patient("吕振", '男', 21, 111.101f, true); // weight不能写成111.1
// PatientA.print();
// 使用toString方法
System.out.println(PatientA);

Patient PatientB = new Patient("张沛", '男', 22, 101.101f, false);
// PatientB.print();
System.out.println(PatientB.toString());
// 等价于System.out.println(PatientB)
System.out.println("PatientB.getId()=" + PatientB.getId());// 注意！！！！连接符不能用,
PatientB.setName("张沛一");
System.out.println("更改后的病人信息为：");
// PatientB.print();
System.out.println(PatientB);
}
}

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