1．toString（）方法
Object類具有一個toString()方法，你創建的每個類都會繼承該方法。它返回對象的一個String表示，並且對於調試非常有幫助。然而對於默認的toString()方法往往不能滿足需求，需要覆蓋這個方法。
toString（）方法將對象轉換為字符串。看以下代碼：
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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);
}
}
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結果：
sample.Orc@11b86e7
sample.Orc@11b86e7
如果去掉注釋，即加入2個toString（）方法后，得到
結果：
Orc12:I'm a Villain and my name is Limburger
Orc19:I'm a Villain and my name is Bob
2．在容器類中使用toString()
編寫一個工具類，用於在控制台輸出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());
}
}
}
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在Hamster類中重寫父類的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;
}
}
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在HamsterMaze類中使用容器類加載Hamster類對象並輸出結果。
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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());
}
}
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結果：
This is Hamster #0
This is Hamster #1
This is Hamster #2
3．一個實現toString()的通用的Bean
在作一個項目時發現,許多bean需要實現toString()方法,就實現一個通用的bean,然后通過其他繼承即可。
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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();
}
}
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測試類
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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());
}
}
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結果
{id:9}