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 （无论是 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");

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/leigt3/archive/2010/01/15/5193091.aspx