public class Test For public static void mainString

例一： public class Test. For { public static void main(String[] arg) { for(int i=1, j=i+10; i<5; i++){ j=i*2; System. out. println("i="+i+" j="+j); } }

例二、 public class Test. For { public static void main(String[] arg) { for(int i=1, j=i+10 ; i<5; i++ , j=i*2) System. out. println("i="+i+" j="+j); } }

例三： public class Test. Break { public static void main(String[] arg) { String output=" "; int i; for(i=1; i<=10; i++){ if (i==5) break; output+=i+" "; } output+="n. Broke out of loop at i ="+1; System. out. println(output); } }

例四： public class Test. Continue { public static void main(String[] arg) { String output=" "; int i; for(i=1; i<=10; i++){ if (i==5) continue; output+=i+" "; } output+="n. Broke out of loop at i ="+1; System. out. println(output); }

以常规方法处理错误 open. Files; if (the. Files. Open) { determine the lenth of the file; if (got. The. File. Length){ allocate that much memory; if (got. Enough. Memory) { read the file into memory; if (read. Failed) error. Code=-1; else error. Code=-2; }else error. Code=-3; }else error. Code=-4 ; }else error. Code=-5;

用异常的形式处理错误 read-File; { try { open. The. File; determine its size; allocate that much memory; close. The. File; }catch(fileopen. Failed) { dosomething; } catch(size. Determine. Failed) {dosomething; } catch(memory. Allocate. Failed){ dosomething; } catch(read. Failed){ dosomething; } catch(file. Close. Failed) { dosomething; } }

4．1．1 异常示例 import java. io. *; class Exception. Demo 1 { 　　public static void main( String args[ ] ) { 　　　　File. Input. Stream fis = new File. Input. Stream( "text" ); 　　　　int b; 　　　　while( (b=fis. read())!=-1 ) { 　　　　 System. out. print( b ); 　　　　　　} 　　　　fis. close( ); 　　　} }//编译时异常

G: javaException. Demo 1. java: 5: unreported exception java. io. File. Not. Found. Exception; must be caught or declared to be thrown { File. Input. Stream fis = new File. Input. Stream( "text" ); ^ G: javaException. Demo 1. java: 7: unreported exception java. io. IOException; must be caught or declared to be thrown while( (b=fis. read())!=-1 ) ^ G: javaException. Demo 1. java: 11: unreported exception java. io. IOException; must be caught or declared to be thrown fis. close( ); ^ 3 errors

class Exception. Demo 2 { 　　public static void main( String args[ ] ) { 　　　　int a = 0; 　　　　System. out. println( 5/a ); 　　} }//运行时异常

常见的异常 • Arithmetic. Exception • Array. Index. Out. Of. Bands. Exception • Array. Store. Exception 如果在使用能够 • IOException • File. Not. Found. Exception 产生异常的方法 而没有捕获和处 • Null. Pointer. Exception 理，将不能通过 • Malformed. URLException 编译 • Number. Format. Exception • Out. Of. Memory. Exception

　try{ 　　　　. . . 　　　}catch( File. Not. Found. Exception e ){ 　　　　System. out. println( e ); 　　　　System. out. println( "message: "+e. get. Message() ); 　　　　e. print. Stack. Trace( System. out ); 　　　}catch( IOException e ){ 　　　　System. out. println( e ); 　　　}

throws子句中同时可以指明多个异常，之 子句中同时可以指明多个异常 间由逗号隔开。例如： 　　public static void main(String args[]) throws IOException, Index. Out. Of. Bounds. Exception { … }

class Throws. Demo 1 { static void procedure() { System. out. println("inside procedure"); throw new Illegal. Access. Exception("demo"); } public static void main(String args[]) { procedure(); } } 　　

1、请问所有的例外类皆继承哪一个类？ 　　 A java. io. Exception B java. lang. Throwable C java. lang. Exception D java. lang. Error

下面的方法是一个不完整的方法，其中的方法 unsafe()会抛出一个IOException，那么在方法的1)处 　　 应加入哪条语句，才能使这个不完整的方法成为一个完 整的方法？ 　　1) 　　2) { if(unsafe()){//do something…} 　　3) else if(safe()){//do the other…} 　　4) } A public IOException method. Name() B public void method. Name() C public void method. Name() throw IOException D public void method. Name() throws IOException E. public void method. Name() throws Exception

如果下列的方法能够正常运行，在控制台上 将显示什么？ 　　 　　public void example(){ 　　　try{ 　　　　　 unsafe(); 　　　　　 System. out. println("Test 1"); 　　　　　} 　　　catch(Safe. Exception e) 　　　　　{System. out. println("Test 2"); } 　　　finally{System. out. println("Test 3"); } 　　　System. out. println("Test 4"); 　　} A Test 1 B Test 2 C Test 3 D Test 4

3、对main（）方法进行修改来捕获procedure（）方 法可能产生的异常。 class Throws. Demo 1 { static void procedure() { System. out. println("inside procedure"); throw new Illegal. Access. Exception("demo"); } public static void main(String args[]) { procedure(); } }