Java类中重写toString方法

默认方法

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(包名+类名)和此对象对应内存的首地址，默认输出例子：

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()

例如：输出类中的变量值：

@Overridepublic String toString(){return "["+this.name+"  "+this.age+"]";}

案例驱动

import java.util.*;public class TreeSetTest {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubSortedSet<Item> parts=new TreeSet<Item>();parts.add(new Item("Toaster", 1234));parts.add(new Item("Widget", 4562));parts.add(new Item("Modem", 9912));System.out.println(parts);SortedSet<Item> sortByDescription=new TreeSet<Item>(new Comparator<Item>(){public int compare(Item a, Item b){String descrA=a.getDescription();String descrB=b.getDescription();return descrA.compareTo(descrB);}});sortByDescription.addAll(parts);System.out.println(sortByDescription);}}class Item implements Comparable<Item>{public Item(String aDescription, int aPartNumber){description=aDescription;partNumber=aPartNumber;}public String getDescription(){return description;}public boolean equals(Object otherObject){if(this==otherObject)return true;if(otherObject==null){return false;}if (getClass()!=otherObject.getClass()){return false;}Item other=(Item)otherObject;return description.equals(other.description)&&partNumber==other.partNumber;}public int hashCode(){return 13*description.hashCode()+17*partNumber;}public int compareTo(Item other){return partNumber-other.partNumber;}private String description;private int partNumber;}

输出为:

[Item@8c9e3a56, Item@d780c206, Item@39c021ba]
[Item@39c021ba, Item@8c9e3a56, Item@d780c206]

Item重载toString()方法后：

import java.util.*;public class TreeSetTest {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubSortedSet<Item> parts=new TreeSet<Item>();parts.add(new Item("Toaster", 1234));parts.add(new Item("Widget", 4562));parts.add(new Item("Modem", 9912));System.out.println(parts);SortedSet<Item> sortByDescription=new TreeSet<Item>(new Comparator<Item>(){public int compare(Item a, Item b){String descrA=a.getDescription();String descrB=b.getDescription();return descrA.compareTo(descrB);}});sortByDescription.addAll(parts);System.out.println(sortByDescription);}}class Item implements Comparable<Item>{public Item(String aDescription, int aPartNumber){description=aDescription;partNumber=aPartNumber;}public String getDescription(){return description;}public String toString(){return "[description="+description+",partNumber="+partNumber+"]";}public boolean equals(Object otherObject){if(this==otherObject)return true;if(otherObject==null){return false;}if (getClass()!=otherObject.getClass()){return false;}Item other=(Item)otherObject;return description.equals(other.description)&&partNumber==other.partNumber;}public int hashCode(){return 13*description.hashCode()+17*partNumber;}public int compareTo(Item other){return partNumber-other.partNumber;}private String description;private int partNumber;}

输出为:

[[description=Toaster,partNumber=1234], [description=Widget,partNumber=4562], [description=Modem,partNumber=9912]]
[[description=Modem,partNumber=9912], [description=Toaster,partNumber=1234], [description=Widget,partNumber=4562]]

动手试一下吧~

转载自：http://blog.csdn.net/tzasd89812/article/details/21371661