內部類與異常類例題
阿新 • • 發佈：2019-02-10
內部類
public class RedCowForm{ static String formName; RedCow cow;//內部類宣告物件 public RedCowForm() { } RedCowForm(String s){ cow=new RedCow(150,112,5000); formName=s; } public void showCowMess() { cow.speak(); } class RedCow{ //內部類的宣告 String cowName="紅牛"; int height,weight,price; public RedCow(int h,int w,int p) { height=h; weight=w; price=p; } void speak(){ System.out.println("偶是"+cowName+"身高:"+height+"cm 體重:"+weight+"kg,生活在"+formName); } }//內部類結束 }// 外嵌類結束
public class exma {
public static void main(String[] args) {
RedCowForm form=new RedCowForm("紅牛農場");
form.showCowMess();
form.cow.speak();
}
}
匿名類
abstract class OutputAlphabet {
public abstract void output();
}public class OutputEnglish extends OutputAlphabet { //輸出英文字母的子類 public void output(){ for(char c='a';c<='z';c++){ System.out.printf("%3c",c); } } }
public class ShowBoard {
void showMess(OutputAlphabet show){ //引數show是OutputAlphabet型別的物件
show.output();
}
}public class Exam { public static void main(String[] args) { ShowBoard borad=new ShowBoard(); borad.showMess(new OutputEnglish());//向引數傳遞OutputAlphabet的子類OutputEnglish物件 borad.showMess(new OutputAlphabet() { public void output() { //引數傳遞OutputAlphabet的匿名子類物件 for(char c='a';c<='z';c++){ System.out.printf("%3c",c); } } } ); } }
和介面有關的匿名類
interface SpeakHello{
void speak();
}
class HelloMachine{
public void turnOn(SpeakHello hello) {
hello.speak();
}
}
public class Exam {
public static void main(String[] args) {
HelloMachine machine=new HelloMachine();
machine.turnOn(new SpeakHello() { //和介面SpeakHello有關的匿名類
public void speak() {
System.out.println("hello,you are welcome!");
}
}
);
machine.turnOn(new SpeakHello() { //和介面SpeakHello有關的匿名類
public void speak() {
System.out.println("你好，歡迎光臨");
}
}
);
}
}
try-catch語句
import java.util.jar.JarException;
public class exam {
public static void main(String[] args) {
int n=0,m=0,t=1000;
try {
m=Integer.parseInt("8888");
n=Integer.parseInt("ab89");//傳送異常，轉向catch
t=7777;//t沒有機會被賦值
} catch (NumberFormatException e) {
System.out.println("發生異常:"+e.getMessage());
}
System.out.println("n="+n+",m="+m+",t="+t);
try {
System.out.println("故意丟擲I/O異常！");
throw new java.io.IOException("我是故意的"); //故意丟擲異常
//System.out.println("這個輸出語句肯定沒有機會執行，必須註釋，否則編譯出錯");
} catch(java.io.IOException e) {
System.out.println("發生異常:"+e.getMessage());
}
}
}
public class BankException extends Exception {
String message;
public BankException(int m,int n) {
message="入賬資金"+m+"是負數或支出"+n+"是正數,不符合系統要求";
}
public String warnMess() {
return message;
}
}public class Bank {
private int money;
public void income(int in,int out) throws BankException {
if(in<=0||out>=0||in+out<=0){
throw new BankException(in, out); //方法丟擲異常，導致方法結束
}
int netIncome=in+out;
System.out.printf("本次計算出得純收入是:%d\n",netIncome);
money=money+netIncome;
}
public int getMoney() {
return money;
}
}
public class Exam {
public static void main(String[] args) {
Bank bank=new Bank();
try {
bank.income(200, -100);
bank.income(300, -100);
bank.income(400, -100);
System.out.printf("銀行目前有%d元\n",bank.getMoney());
bank.income(200,100);
bank.income(99999,-100);
}
catch (BankException e) {
System.out.println("計算收益得過程出現如下問題");
System.out.println(e.warnMess());
}
System.out.printf("銀行目前有%d元\n",bank.getMoney());
}
}import java.util.*;
public class exam {
public static void main(String[] args) {
int [] score={-120,98,89,120,99};
int sum=0;
for(int number:score){
assert number>=0:"負數不能是成績";
sum=sum+number;
}
System.out.println("總成績:"+sum);
}
}
應用舉例
public class DangerException extends Exception {
final String message="超重";
public String warnMess() {
return message;
}
}
public class CargoBoat {
int realContent; //裝載的重量
int maxContent; //最大裝載量
public void setMaxContent(int c) {
maxContent=c;
}
public void loading(int m)throws DangerException {
realContent+=m;
if(realContent>maxContent){
realContent-=m;
throw new DangerException();
}
System.out.println("目前裝載了"+realContent+"噸貨物");
}
}public class Exam {
public static void main(String[] args) {
CargoBoat ship=new CargoBoat();
ship.setMaxContent(1000);
int m=600;
try {
ship.loading(m);
m=400;
ship.loading(m);
m=347;
ship.loading(m);
m=555;
ship.loading(m);
}
catch (DangerException e) {
System.out.println(e.warnMess());
System.out.println("無法再裝載重量是"+m+"噸的集裝箱");
}
finally{
System.out.println("貨物將正點啟航");
}
}
}
習題
class Cry{
public void cry() {
System.out.println("大家好");
}
}
public class E {
public static void main(String[] args) {
Cry hello=new Cry(){
public void cry(){
System.out.println("大家好,祝工作順利！");
}
};
hello.cry();
}
}
interface Com{
public void speak();
}
public class E {
public static void main(String[] args) {
Com p=new Com(){
public void speak(){
System.out.println("p是介面變數");
}
};
p.speak();
}
}
import java.io.IOException;
import org.omg.CORBA.PUBLIC_MEMBER;
public class E {
public static void main(String[] args) {
try{
methodA();
}
catch(IOException e){
System.out.println("你好");
return ;
}
finally{
System.out.println(" fine thanks");
}
}
public static Void methodA() throws IOException{
throw new IOException();
}
}
class RedCowForm{
static class RedCow{ //靜態內部類是外嵌類中的一種靜態資料型別
void speak(){
System.out.println("我是紅牛");
}
}
}
public class E {
public static void main(String[] args) {
RedCowForm.RedCow redCow= new RedCowForm.RedCow();//如果RedCow不是靜態類此程式碼非法
redCow.speak();
}
}