finally 和 return的执行关系，try..catch..finally_finally后的return会执行吗-优快云博客

结论

程序执行到return时

如果返回的是基础变量，如Int，String等，返回值，即最终返回。
如果返回的是复合变量，如Map，自定义类型，返回引用[地址]，return之后仍然会被改变。

finally的功能是处理一些善后工作，比如关闭IO，清楚缓存等。

通常不使用finally做赋值操作，容易引起混乱，如果finally里有return会执行。

基础类型Int，返回值

@Slf4j
public class FinallyandReturn {
	public static void main(String[] args) {
		log.info(""+finallyAndReturn());
	}
	public static int finallyAndReturn() {
		int a  = 10;
		try {
			a = 20;
			a = a/0;
			return a;
		}catch(Exception e) {
			a = 30;
			return a;
		}finally {
			log.info("I'm running finally");
			a = 40;
		}
	}
}

结果：30

基础类型String，返回值

@Slf4j
public class FinallyandReturn {
	public static void main(String[] args) {
		log.info(finallyAndReturn().toString());
	}
	public static String finallyAndReturn() {
		String str  = "10";
		Map map = new HashMap();
		try {
			str = "20";
			str = ""+ 10/0;
			return str;
		}catch(Exception e) {
			str = "30";
			return str;
		}finally {
			log.info("I'm running finally");
			str = "40";
		}
	}
}

结果：30

基础类型StringBuffer，返回值

@Slf4j
public class FinallyandReturn {
	public static void main(String[] args) {
		log.info(finallyAndReturn().toString());
	}
	public static String finallyAndReturn() {
		StringBuffer sb = new StringBuffer();
		sb.append("10");
		Map map = new HashMap();
		try {
			sb.delete(0, sb.length()).append("20");
			sb.append(""+ 10/0);
			return sb.toString();
		}catch(Exception e) {
			sb.delete(0, sb.length()).append("30");
			return sb.toString();
		}finally {
			log.info("I'm running finally");
			sb.delete(0, sb.length()).append("40");
		}
	}
}

结果：30

复合类型Map，返回引用

@Slf4j
public class FinallyandReturn {
	public static void main(String[] args) {
		log.info(finallyAndReturn().toString());
	}
	public static Map finallyAndReturn() {
		int a  = 10;
		Map map = new HashMap();
		try {
			a = 20;
			a = a/0;
			map.put("a",a);
			return map;
		}catch(Exception e) {
			a = 30;
			map.put("a",a);
			return map;
		}finally {
			log.info("I'm running finally");
			a = 40;
			map.put("a",a);
		}
	}
}

结果： {a = 40}

自定义类型，返回引用

@Slf4j
public class FinallyandReturn {
	public static void main(String[] args) {
		log.info(finallyAndReturn().name);
	}
	public static Data finallyAndReturn() {
		Data data = new Data();
	   data.setName("10");;
		try {
			data.setName("20");
			data.setName(""+ 10/0);
			return data;
		}catch(Exception e) {
			data.setName("30");
			return data;
		}finally {
			log.info("I'm running finally");
			data.setName("40");
		}
	}
	static class Data{
		String name;
		void setName(String name){
			this.name = name;
		}
	}
}

结果：name=40

执行了finally 里的return

@Slf4j
public class FinallyandReturn {
	public static void main(String[] args) {
		log.info(finallyAndReturn().toString());
	}
	public static Map finallyAndReturn() {
		int a  = 10;
		Map map = new HashMap();
		try {
			a = 20;
			a = a/0;
			map.put("a",a);
			return map;
		}catch(Exception e) {
			a = 30;
			map.put("a",a);
			return map;
		}finally {
			log.info("I'm running finally");
			a = 40;
			map.put("a",a);
			return new HashMap();
		}
	}
}

结果：{}