try-catch-finally陷阱

package com.jjyy.test;

import org.junit.Test;

public class BasicTest {

@Test
public void test01() {
System.out.println(test_01());//try
}

@Test
public void test02() {
System.out.println(test_02());//finally
}

@Test
public void test03() {
System.out.println(test_03());//catch
}

@Test
public void test04() {
System.out.println(test_04());//finally
}

@Test
public void test05() {
System.out.println(test_05());//java.lang.NumberFormatException
}

@Test
public void test06() {
System.out.println(test_06());//finally
}

@Test
public void test07() {
System.out.println(test_07());//java.lang.NumberFormatException

}

@Test
public void test08() {
System.out.println(test_08());//finally
}

@Test
public void test09() {
System.out.println(test_09());//java.lang.NullPointerException
}

public String test_01() {
String t = "";
try {
t = "try";
return t;
} catch (Exception e) {
// result = "catch";
t = "catch";
return t;
} finally {
t = "finally";
}
}

@SuppressWarnings("finally")
public String test_02() {
String t = "";

try {
t = "try";
return t;
} catch (Exception e) {
// result = "catch";
t = "catch";
return t;
} finally {
t = "finally";
return t;
}
}

public String test_03() {
String t = "";
try {
t = "try";
Integer.parseInt(null);
return t;
} catch (Exception e) {
t = "catch";
return t;
} finally {
t = "finally";
// System.out.println(t);
// return t;
}
}

@SuppressWarnings("finally")
public String test_04() {
String t = "";

try {
t = "try";
Integer.parseInt(null);
return t;
} catch (Exception e) {
t = "catch";
return t;
} finally {
t = "finally";
return t;
}
}

public String test_05() {
String t = "";

try {
t = "try";
Integer.parseInt(null);
return t;
} catch (Exception e) {
t = "catch";
Integer.parseInt(null);
return t;
} finally {
t = "finally";
//return t;
}
}

@SuppressWarnings("finally")
public String test_06() {
String t = "";

try {
t = "try";
Integer.parseInt(null);
return t;
} catch (Exception e) {
t = "catch";
Integer.parseInt(null);
return t;
} finally {
t = "finally";
return t;
}
}

public String test_07() {
String t = "";

try {
t = "try";
Integer.parseInt(null);
return t;
} catch (NullPointerException e) {
t = "catch";
return t;
} finally {
t = "finally";
}
}

@SuppressWarnings("finally")
public String test_08() {
String t = "";

try {
t = "try";
Integer.parseInt(null);
return t;
} catch (NullPointerException e) {
t = "catch";
return t;
} finally {
t = "finally";
return t;
}
}

@SuppressWarnings("finally")
public String test_09() {
String t = "";

try {
t = "try";return t;
} catch (Exception e) {
t = "catch";
return t;
} finally {
t = "finally";
String.valueOf(null);
return t;
}
}
/*
对以上所有的例子进行总结

1 try、catch、finally语句中，在如果try语句有return语句，则返回的之后当前try中变量此时对应的值，此后对变量做任何的修改，都不影响try中return的返回值

2 如果finally块中有return 语句，则返回try或catch中的返回语句忽略。

3 如果finally块中抛出异常，则整个try、catch、finally块中抛出异常

所以使用try、catch、finally语句块中需要注意的是

1   尽量在try或者catch中使用return语句。通过finally块中达到对try或者catch返回值修改是不可行的。

2 finally块中避免使用return语句，因为finally块中如果使用return语句，会显示的消化掉try、catch块中的异常信息，屏蔽了错误的发生

3 finally块中避免再次抛出异常，否则整个包含try语句块的方法回抛出异常，并且会消化掉try、catch块中的异常

*/
}