从C++转java,在使用函数传对象时,碰到一点问题,今天特意验证了一下:
public class App { public static void doubleTest(double d) { d=8.0; System.out.println( "[INNER doubleTest]double:"+d); } public static void DoubleTest(Double dd) { dd=8.0; System.out.println( "[INNER DoubleTest]Double:"+dd); } public static void ObjectTest(ObjectChange obj) { obj = new ObjectChange(5); System.out.println( "[INNER ObjectTest]Object:"+obj.getTT()); obj.setTT(8); System.out.println( "[INNER ObjectTest]Object:"+obj.getTT()); } public static void ObjectChangeTest(ObjectChange obj) { obj.setTT(8); System.out.println( "[INNER ObjectChangeTest]Object:"+obj.getTT()); obj = new ObjectChange(5); System.out.println( "[INNER ObjectChangeTest]Object:"+obj.getTT()); obj.setTT(6); System.out.println( "[INNER ObjectChangeTest]Object:"+obj.getTT()); } public static void main( String[] args ) { System.out.println( "Source:" ); double d1=1; Double d2=2.0; ObjectChange obj1 = new ObjectChange(1); System.out.println( "double:"+d1+" Double:"+d2 +" Object:"+ obj1.getTT()); System.out.println( "After:" ); doubleTest(d1); DoubleTest(d2); ObjectTest(obj1); System.out.println( "double:"+d1+" Double:"+d2 +" Object:"+ obj1.getTT()); ObjectChangeTest(obj1); System.out.println( "Object:"+ obj1.getTT()); } }
程序输出结果:
总结:
obj在函数体内作为临时变量,可读取对象内容,采用“=”(赋值运算符)改变的是临时对象的内容,赋值后,再操作的也是临时对象的内容;
只有在赋值前调用对象的成员方法(setTT())才能真正改变obj对象的内容;