代码的等价性

最新推荐文章于 2022-10-23 21:09:30 发布

idevcod

最新推荐文章于 2022-10-23 21:09:30 发布

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分类专栏： Java

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本文探讨了代码片段之间的等价性问题，特别是在处理条件语句时的陷阱。以两个不等效的代码片段为例，指出在代码片段2中，如果file1.delete()返回true，后续的file2.delete()和file3.delete()将不会执行，强调编程中应避免此类逻辑错误。

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代码片段1:

boolean result1 = file1.delete();
boolean result2 = file2.delete();
boolean result3 = file3.delete();
 
if( result1 || result2 || result3)
{
    //do something ...
}

代码片段2:

if( file1.delete() || file2.delete() || file3.delete())
{
    //do something ...
}

上述两个代码片段是不等效的.在代码片段2中,如果file1.delete()返回true,那么后面的file2.delete()与file3.delete()将不会执行.在编程中需要避免这种陷阱!!!

完整示例如下：

public class LogicTest {
    public void test1() {
        System.out.println("call test1 begin ...");
 
        Logic logic = new Logic();
        boolean result1 = changeA(logic);
        boolean result2 = changeB(logic);
        boolean result3 = changeC(logic);
 
        if (result1 || result2 || result3) {
            System.out.println(logic.getA());
            System.out.println(logic.getB());
            System.out.println(logic.getC());
        }
 
        System.out.println("call test1 end ...");
    }
 
    public void test2() {
        System.out.println("call test2 begin ...");
 
        Logic logic = new Logic();
        if (changeA(logic) || changeB(logic) || changeC(logic)) {
            System.out.println(logic.getA());
            System.out.println(logic.getB());
            System.out.println(logic.getC());
        }
 
        System.out.println("call test2 end ...");
    }
 
    public boolean changeA(Logic logic) {
        logic.setA(5);
        return true;
    }
 
    public boolean changeB(Logic logic) {
        logic.setB(6);
        return true;
    }
 
    public boolean changeC(Logic logic) {
        logic.setC(7);
        return true;
    }
 
    class Logic {
        private int a;
        private int b;
        private int c;
 
        public int getA() {
            return a;
        }
 
        public void setA(int a) {
            this.a = a;
        }
 
        public int getB() {
            return b;
        }
 
        public void setB(int b) {
            this.b = b;
        }
 
        public int getC() {
            return c;
        }
 
        public void setC(int c) {
            this.c = c;
        }
    }
 
    public static void main(String[] args) {
        new LogicTest().test1();
        System.out.println();
        new LogicTest().test2();
    }
}

输出结果为：

call test1 begin ...
5
6
7
call test1 end ...
 
call test2 begin ...
5
0
0
call test2 end ...