Java之---测试try、catch、finally、return的顺序

  总结执行顺序：
  1、先执行try/catch
  2、在执行finally
  3、执行return

测试代码如下：

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

/**
 * 测试try catch finally return的执行顺序
 * 执行顺序：
 * 1、先执行try/catch
 * 2、在执行finally
 * 3、执行return
 * @author Administrator
 *
 */
public class TestReadFile {
	public static void main(String[] args) {
		String str = new TestReadFile().OpenFile();
		System.out.println(str);
	}
	String OpenFile(){
		try {
			System.out.println("aaa");
			FileInputStream fis = new FileInputStream("d:/a.txt");
			int a = fis.read();
			System.out.println("bbb");
			return "step1";
		} catch (FileNotFoundException e) {
			System.out.println("cathching!");
			// TODO Auto-generated catch block
			e.printStackTrace();//先确定返回的值，并不会直接结束运行！
			return "step2";
		} catch(IOException e) {
			e.printStackTrace();
			return "step3";
		}finally {
			System.out.println("finally!!!!!");
			//return "fff";
			//不要再在finally中使用return！
		}
	}
}

 

正常执行的结果（从try块return）：
aaa
bbb
finally!!!!!
step1

 

非正常执行的结果（从catch块return）：
aaa
cathching!
java.io.FileNotFoundException: d:\aasa.txt (系统找不到指定的文件。)
	at java.base/java.io.FileInputStream.open0(Native Method)
	at java.base/java.io.FileInputStream.open(Unknown Source)
	at java.base/java.io.FileInputStream.<init>(Unknown Source)
	at java.base/java.io.FileInputStream.<init>(Unknown Source)
	at TestReadFile.OpenFile(TestReadFile.java:22)
	at TestReadFile.main(TestReadFile.java:16)
finally!!!!!
step2

 

finally块中增添return正常执行（try）的结果：
aaa
bbb
finally!!!!!
fff

 

finally块中增添return非正常执行（catch）的结果：
aaa
cathching!
finally!!!!!
fff
java.io.FileNotFoundException: d:\aaa.txt (系统找不到指定的文件。)
	at java.base/java.io.FileInputStream.open0(Native Method)
	at java.base/java.io.FileInputStream.open(Unknown Source)
	at java.base/java.io.FileInputStream.<init>(Unknown Source)
	at java.base/java.io.FileInputStream.<init>(Unknown Source)
	at TestReadFile.OpenFile(TestReadFile.java:22)
	at TestReadFile.main(TestReadFile.java:16)