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  • Java中的try、catch、finally块简单的解析

    package com.wangzhu;
    
    import java.util.HashMap;
    import java.util.Map;
    
    /**
     * 在try、catch、finally块中,若try中有return语句,则返回try中变量的值,<br/>
     * 不管try块外是否对该变量进行了修改, 都不影响try中return的返回值。<br/>
     * 若finally中有return语句,则忽略try、catch块中的return语句。<br/>
     * 若finally中抛出异常,则整个try-catch-finally块中抛出异常。<br/>
     * 
     * 注意:<br/>
     * 尽量在try或者catch中使用return语句,通过finally快中达到对try或者catch返回值的修改是不可行的。<br/>
     * finally块中避免使用return语句,因为finally快中如果使用return语句,<br/>
     * 会显示的消化掉try、catch块中的异常信息, 屏蔽了错误的发生。<br/>
     * finally块中皮面再次抛出异常,否则整个try-catch-finally块的方法抛出异常,并会消化掉try、catch块中的异常。<br/>
     * 
     * @author wangzhu2014-7-20下午8:48:43
     * 
     */
    public class CatchDemo1 {
        /**
         * 返回:try
         * 
         * @return
         */
        public static String test() {
            String str = "";
            try {
                str = "try";
                return str;
            } catch (Exception e) {
                str = "catch";
                return str;
            } finally {
                str = "finally";
            }
        }
    
        /**
         * 返回:finally
         * 
         * @return
         */
        public static String test1() {
            String str = "";
            try {
                str = "try";
                return str;
            } catch (Exception e) {
                str = "catch";
                return str;
            } finally {
                str = "finally";
                return str;
            }
        }
    
        /**
         * 返回:catch
         * 
         * @return
         */
        public static String test2() {
            String str = "";
            try {
                str = "try";
                Integer.parseInt(null);
                return str;
            } catch (Exception e) {
                str = "catch";
                return str;
            } finally {
                str = "finally";
            }
        }
    
        /**
         * 返回:finally
         * 
         * @return
         */
        public static String test3() {
            String str = "";
            try {
                str = "try";
                Integer.parseInt(null);
            } catch (Exception e) {
                str = "catch";
                return str;
            } finally {
                str = "finally";
                return str;
            }
        }
    
        /**
         * 返回:finally
         * 
         * @return
         */
        public static String test4() {
            String str = "";
            try {
                str = "try";
                Integer.parseInt(null);
                return str;
            } catch (Exception e) {
                str = "catch";
                Integer.parseInt(null);
                return str;
            } finally {
                str = "finally";
                // 若去掉return语句则最后会报异常
                return str;
            }
        }
    
        /**
         * 返回:finally
         * 
         * @return
         */
        public static String test5() {
            String str = "";
            try {
                str = "try";
                Integer.parseInt(null);
                return str;
            } catch (NullPointerException e) {
                str = "catch";
                return str;
            } finally {
                str = "finally";
                // 若去掉return语句则最后会报异常
                return str;
            }
        }
    
        public static String test6(Map<String, Object> map) {
            String str = "";
            try {
                str = "try";
                map.put(str, str);
                Integer.parseInt(null);
                return str;
            } catch (NullPointerException e) {
                str = "catch";
                map.put(str, str);
                return str;
            } finally {
                str = "finally";
                map.put(str, str);
                // 若去掉return语句则最后会报异常
                return str;
            }
        }
    
        public static void main(String[] args) {
            System.out.println("try: " + CatchDemo1.test());
            System.out.println("finally: " + CatchDemo1.test1());
            System.out.println("catch: " + CatchDemo1.test2());
            System.out.println("finally: " + CatchDemo1.test3());
            System.out.println("finally: " + CatchDemo1.test4());
            System.out.println("finally: " + CatchDemo1.test5());
            Map<String, Object> map = new HashMap<String, Object>();
            System.out.println("finally: " + CatchDemo1.test6(map));
            for (String key : map.keySet()) {
                System.out.println(key + "===" + map.get(key));
            }
        }
    }
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  • 原文地址:https://www.cnblogs.com/xiaoxian1369/p/3857309.html
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