Java类中重写toString方法，java类重写tostring

Java类中重写toString方法，java类重写tostring

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：

@Override
public 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 stub
		SortedSet<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 stub
		SortedSet<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