1、创建自定义异常
一个英雄攻击另一个英雄的时候，如果发现另一个英雄已经挂了，就会抛出EnemyHeroIsDeadException
创建一个类EnemyHeroIsDeadException，并继承Exception
提供两个构造方法
- 无参的构造方法
- 带参的构造方法，并调用父类的对应的构造方法
class EnemyHeroIsDeadException extends Exception{
public EnemyHeroIsDeadException(){
}
public EnemyHeroIsDeadException(String msg){
super(msg);
}
}
2、抛出自定义异常
在Hero的attack方法中，当发现敌方英雄的血量为0的时候，抛出该异常
- 创建一个EnemyHeroIsDeadException实例
- 通过throw 抛出该异常
- 当前方法通过 throws 抛出该异常
在外部调用attack方法的时候，就需要进行捕捉，并且捕捉的时候，可以通过e.getMessage() 获取当时出错的具体原因
package charactor;
public class Hero {
public String name;
protected float hp;
public void attackHero(Hero h) throws EnemyHeroIsDeadException{
if(h.hp == 0){
throw new EnemyHeroIsDeadException(h.name + " 已经挂了,不需要施放技能" );
}
}
public String toString(){
return name;
}
class EnemyHeroIsDeadException extends Exception{
public EnemyHeroIsDeadException(){
}
public EnemyHeroIsDeadException(String msg){
super(msg);
}
}
public static void main(String[] args) {
Hero garen = new Hero();
garen.name = "盖伦";
garen.hp = 616;
Hero teemo = new Hero();
teemo.name = "提莫";
teemo.hp = 0;
try {
garen.attackHero(teemo);
} catch (EnemyHeroIsDeadException e) {
// TODO Auto-generated catch block
System.out.println("异常的具体原因:"+e.getMessage());
e.printStackTrace();
}
}
}
3、练习：自定义异常
对MyStringBuffer的插入和删除方法中的边界条件判断，用抛出异常来解决
例: insert(int pos, String b) , 当pos 是负数的时候，抛出自定义异常
需要实现自定义两种异常
IndexIsNagetiveException 下标为负异常
IndexIsOutofRangeException 下标超出范围异常
以下是需要调用这些异常的场景：
- pos<0
抛出 IndexIsNagetiveException
- pos>length
抛出 IndexIsOutofRangeException
- null==b
抛出 NullPointerException
- start<0
抛出 IndexIsNagetiveException
- start>length
抛出 IndexIsOutofRangeException
- end<0
抛出 IndexIsNagetiveException
- end>length
抛出 IndexIsOutofRangeException
- start>=end
抛出 IndexIsOutofRangeException
注意： 接口IStringBuffer中声明的方法需要抛出异常
package StringBuffer;
public class MyStringBuffer2 {
// 数组容量
int capacity = 16;
int length = 0;
char[] value;
public MyStringBuffer2() {
value = new char[capacity];
}
public MyStringBuffer2(String str) {
this();
if (null == str)
return;
if (capacity < str.length()) {
capacity = value.length * 2;
value = new char[capacity];
}
if (capacity >= str.length())
System.arraycopy(str.toCharArray(), 0, value, 0, str.length());
length = str.length();
}
public void append(String str) throws Exception{
insert(length, str);
}
public void append(char c) throws Exception{
append(String.valueOf(c));
}
public void insert(int pos, char b) throws Exception{
insert(pos, String.valueOf(b));
}
public void insert(int pos, String b) throws Exception{
// 边界判断
if(pos<0)
throw new IndexIsNagetiveException("下标为负异常！！");
if(pos>length)
throw new IndexIsOutofRangeException("下标超出范围异常！！");
if(null==b)
throw new NullPointerException("空字符串异常！！");
// 扩容
while(length+b.length()>capacity) {
capacity = (int)((length+b.length())*1.5);
char[] newValue = new char[capacity];
System.arraycopy(value, 0, newValue, 0, length);
value = newValue;
}
char[] cs = b.toCharArray();
//先把已经存在的数据往后移
System.arraycopy(value, pos, value,pos+ cs.length, length-pos);
//把要插入的数据插入到指定位置
System.arraycopy(cs, 0, value, pos, cs.length);
length = length+cs.length;
}
public void delete(int start) throws Exception{
delete(start,length);
}
public void delete(int start, int end) throws Exception{
if(start<0||end<0)
throw new IndexIsNagetiveException("下标为负异常");
if(start>length||end>length||start>=end)
throw new IndexIsOutofRangeException("下标超出范围异常");
System.arraycopy(value, end, value, start, length-end);
length-=end-start;
}
public void reverse() {
for(int i = 0;i<length/2;i++) {
char temp = value[i];
value[i] = value[length-i-1];
value[length-i-1] = temp;
}
}
public int length() {
return length;
}
public String toString() {
char[] realValue = new char[length];
System.arraycopy(value, 0, realValue, 0, length);
return new String(realValue);
}
class IndexIsNagetiveException extends Exception {
public IndexIsNagetiveException() {
}
public IndexIsNagetiveException(String msg) {
super (msg);
}
}
class IndexIsOutofRangeException extends Exception{
public IndexIsOutofRangeException() {
}
public IndexIsOutofRangeException(String msg) {
super (msg);
}
}
public static void main(String[] args) {
MyStringBuffer2 str1 = new MyStringBuffer2("终极无敌嗜血封魔手！！");
System.out.println(str1);
try {
str1.insert(-1, '1');
} catch (Exception e) {
// TODO: handle exception
System.out.println("具体异常为:"+e.getMessage());
e.printStackTrace();
}
try {
str1.delete(1,2424);
} catch (Exception e) {
// TODO: handle exception
System.out.println("具体异常为:"+e.getMessage());
e.printStackTrace();
}
}
}
4、参考链接
