Java中try,return ,finally,throw使用总结
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转载地址:http://blog.csdn.net/leigt3/article/details/5193091
Java 中 try , return , finally , throw 使用总结:
(1) 当 try 中抛出异常且 catch 中有 return 语句, finally 中没有 return 语句, java 先执行 catch 中非 return语句,再执行 finally 语句,最后执行 catch 中 return 语句。详见情况一。
(2) 当 try 中抛出异常且 catch 中有 return 语句, finally 中也有 return 语句, java 先执行 catch 中非 return语句,再执行 finally 中非 return 语句,最后执行 finally 中 return 语句,函数返回值为 finally 中返回的值。详见情况二。
(3) Throw (无能是 catch 中还是非 catch 中)后面不能再跟 code ,否则编译不能通过。详见下面情况三,四,五。
Return , finally 总结:
情况一,代码如下:
public class Test {
public int testTry(){
FileInputStream fi=null;
try{
fi=new FileInputStream("");
}catch(FileNotFoundException fnfe){
System.out.println("this is FileNotFoundException");
return 1;
}catch(SecurityException se){
System.out.println("this is SecurityException");
}finally{
System.out.println("this is finally");
}
return 0;
}
public static void main(String[] args) {
Test t= new Test();
System. out .println(t.testTry());
}
}
Output :
this is FileNotFoundException
this is finally
1
情况二,代码修改如下:
public class Test {
public int testTry(){
FileInputStream fi=null;
try{
fi=new FileInputStream("");
}catch(FileNotFoundException fnfe){
System.out.println("this is FileNotFoundException");
return 1;
}catch(SecurityException se){
System.out.println("this is SecurityException");
}finally{
System.out.println("this is finally");
return 3;
}
//return 0;
}
public static void main(String[] args) {
Test t= new Test();
System. out .println(t.testTry());
}
}
Output :
this is FileNotFoundException
this is finally
3
----------------------------------------------------
Return throw 总结:
情况三:
public class Test {
public static void main(String[] args) {
Test t=new Test();
try{
System.out.println(t.testTry());
}catch(Exception e){
System.out.println("this is exception");
}
}
public int testTry()throws Exception{
FileInputStream fi=null;
try{
fi=new FileInputStream("");
}catch(FileNotFoundException fnfe){
//System.out.println("this is FileNotFoundException");
throw new Exception();
return 1;
}catch(SecurityException se){
System.out.println("this is SecurityException");
}finally{
System.out.println("this is finally");
}
return 0;
}
}
>javac Test.java
Test.java:22: 无法访问的语句
Return 1;
情况四:
public class Test {
public static void main(String[] args) {
Test t=new Test();
try{
System.out.println(t.testTry());
}catch(Exception e){
System.out.println("this is exception");
}
}
public int testTry()throws Exception{
FileInputStream fi=null;
try{
fi=new FileInputStream("");
}catch(FileNotFoundException fnfe){
//System.out.println("this is FileNotFoundException");
throw new Exception();
System.out.println("after throw exception");
// return 1;
}catch(SecurityException se){
System.out.println("this is SecurityException");
}finally{
System.out.println("this is finally");
}
return 0;
}
}
>javac Test.java
Test.java:22: 无法访问的语句
System.out.println("this is SecurityException");
情况五:
public class Test {
public static void main(String[] args) {
Test t=new Test();
try{
t.testTry();
}catch(Exception e){
System.out.println("this is exception");
}
}
public void testTry()throws Exception{
throw new Exception();
System.out.println("this is testTry method");
}
}
>javac Test.java
Test.java:22: 无法访问的语句
System.out.println("this is testTry method");
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