1．toString（）方法
Object类具有一个toString()方法，你创建的每个类都会继承该方法。它返回对象的一个String表示，并且对于调试非常有帮助。然而对于默认的toString()方法往往不能满足需求，需要覆盖这个方法。
toString（）方法将对象转换为字符串。看以下代码：
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package sample; class Villain { private String name; protected void set(String nm) { name = nm; } public Villain(String name) { this.name = name; } public String toString() { return "I'm a Villain and my name is " + name; } } public class Orc extends Villain { private int orcNumber; public Orc(String name, int orcNumber) { super(name); this.orcNumber = orcNumber; } public void change(String name, int orcNumber) { set(name); this.orcNumber = orcNumber; } public String toString() { return "Orc" + orcNumber + ":" + super.toString(); } public static void main(String[] args) { Orc orc = new Orc("Limburger", 12); System.out.println(orc); orc.change("Bob", 19); System.out.println(orc); } } |
结果：
sample.Orc@11b86e7
sample.Orc@11b86e7
如果去掉注释，即加入2个toString（）方法后，得到
结果：
Orc12:I'm a Villain and my name is Limburger
Orc19:I'm a Villain and my name is Bob
2．在容器类中使用toString()
编写一个工具类，用于在控制台输出Iterator。
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import java.util.Iterator; public class Printer { static void printAll(Iterator e){ while(e.hasNext()){ System.out.println(e.next()); } } } |
在Hamster类中重写父类的toString（）方法。
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public class Hamster { private int hamsterNumber; public Hamster(int hamsterNumber){ this.hamsterNumber=hamsterNumber; } public String toString(){ return "This is Hamster #"+hamsterNumber; } } |
在HamsterMaze类中使用容器类加载Hamster类对象并输出结果。
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import java.util.ArrayList; import java.util.List; public class HamsterMaze { @SuppressWarnings("unchecked") public static void main(String[] args){ List list=new ArrayList(); for(int i=0;i<3;i++) list.add(new Hamster(i)); Printer.printAll(list.iterator()); } } |
结果：
This is Hamster #0
This is Hamster #1
This is Hamster #2
3．一个实现toString()的通用的Bean
在作一个项目时发现,许多bean需要实现toString()方法,就实现一个通用的bean,然后通过其他继承即可。
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import java.lang.reflect.Field; public class BaseBean { public String toString() { StringBuffer sb = new StringBuffer(); try { Class t = this.getClass(); Field[] fields = t.getDeclaredFields(); for (int i = 0; i < fields.length; i++) { Field field = fields[i]; field.setAccessible(true); sb.append("{"); sb.append(field.getName()); sb.append(":"); if (field.getType() == Integer.class) { sb.append(field.getInt(this)); } else if (field.getType() == Long.class) { sb.append(field.getLong(this)); } else if (field.getType() == Boolean.class) { sb.append(field.getBoolean(this)); } else if (field.getType() == char.class) { sb.append(field.getChar(this)); } else if (field.getType() == Double.class) { sb.append(field.getDouble(this)); } else if (field.getType() == Float.class) { sb.append(field.getFloat(this)); } else sb.append(field.get(this)); sb.append("}"); } } catch (Exception e) { e.printStackTrace(); } return sb.toString(); } } |
测试类
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public class TestBean extends BaseBean { private int id; public int getId() { return id; } public void setId(int id) { this.id = id; } public static void main(String[] args) { TestBean testBean = new TestBean(); testBean.setId(9); System.out.println(testBean.toString()); } } |
结果
{id:9}