java tostring方法重写代码示例
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()
importjava.util.*;
publicclassTreeSetTest{
/**
*@paramargs
*/
publicstaticvoidmain(String[]args){
//TODOAuto-generatedmethodstub
SortedSet- parts=newTreeSet
- ();
parts.add(newItem("Toaster",1234));
parts.add(newItem("Widget",4562));
parts.add(newItem("Modem",9912));
System.out.println(parts);
SortedSet
- sortByDescription=newTreeSet
- (new
Comparator
- ()
{
publicintcompare(Itema,Itemb)
{
StringdescrA=a.getDescription();
StringdescrB=b.getDescription();
returndescrA.compareTo(descrB);
}
});
sortByDescription.addAll(parts);
System.out.println(sortByDescription);
}
}
classItemimplementsComparable
-
{
publicItem(StringaDescription,intaPartNumber)
{
description=aDescription;
partNumber=aPartNumber;
}
publicStringgetDescription()
{
returndescription;
}
publicbooleanequals(ObjectotherObject)
{
if(this==otherObject)
returntrue;
if(otherObject==null)
{
returnfalse;
}
if(getClass()!=otherObject.getClass())
{
returnfalse;
}
Itemother=(Item)otherObject;
returndescription.equals(other.description)&&
partNumber==other.partNumber;
}
publicinthashCode()
{
return13*description.hashCode()+17*partNumber;
}
publicintcompareTo(Itemother)
{
returnpartNumber-other.partNumber;
}
privateStringdescription;
privateintpartNumber;
}
输出为:
[Item@8c9e3a56,Item@d780c206,Item@39c021ba] [Item@39c021ba,Item@8c9e3a56,Item@d780c206]
Item重载toString()方法后：
importjava.util.*;
publicclassTreeSetTest{
/**
*@paramargs
*/
publicstaticvoidmain(String[]args){
//TODOAuto-generatedmethodstub
SortedSet- parts=newTreeSet
- ();
parts.add(newItem("Toaster",1234));
parts.add(newItem("Widget",4562));
parts.add(newItem("Modem",9912));
System.out.println(parts);
SortedSet
- sortByDescription=newTreeSet
- (new
Comparator
- ()
{
publicintcompare(Itema,Itemb)
{
StringdescrA=a.getDescription();
StringdescrB=b.getDescription();
returndescrA.compareTo(descrB);
}
});
sortByDescription.addAll(parts);
System.out.println(sortByDescription);
}
}
classItemimplementsComparable
-
{
publicItem(StringaDescription,intaPartNumber)
{
description=aDescription;
partNumber=aPartNumber;
}
publicStringgetDescription()
{
returndescription;
}
publicStringtoString()
{
return"[description="+description
+",partNumber="+partNumber+"]";
}
publicbooleanequals(ObjectotherObject)
{
if(this==otherObject)
returntrue;
if(otherObject==null)
{
returnfalse;
}
if(getClass()!=otherObject.getClass())
{
returnfalse;
}
Itemother=(Item)otherObject;
returndescription.equals(other.description)&&
partNumber==other.partNumber;
}
publicinthashCode()
{
return13*description.hashCode()+17*partNumber;
}
publicintcompareTo(Itemother)
{
returnpartNumber-other.partNumber;
}
privateStringdescription;
privateintpartNumber;
}
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]]
总结
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