Java的数据通过操作符来操作。
几个简单理解:
1.别名问题:
eg1:两个实例t1,t2,对于每个对象都赋予了不同的值,然后将t2赋给t1,接着修改t1,可能我们总以为t1,t2相互独立,但是t1,t2包含相同的引用,指向相同的对象,所以t2也随之改变。
class Tank{
int level;
}
public class bie {
public static void main(String args[]){
Tank t1 = new Tank();
Tank t2 = new Tank();
t1.level = 9;
t2.level = 47;
System.out.println("1:t1.level="+t1.level+" t2.level:"+t2.level);
t1 = t2;
System.out.println("1:t1.level="+t1.level+" t2.level:"+t2.level);
t1.level = 27;
System.out.println("1:t1.level="+t1.level+" t2.level:"+t2.level);
}
}
output:
1:t1.level=9 t2.level:47
1:t1.level=47 t2.level:47
1:t1.level=27 t2.level:27
eg2:避免别名问题,我们就需要让t1,t2独立
class Tank{
int level;
}
public class bie {
public static void main(String args[]){
Tank t1 = new Tank();
Tank t2 = new Tank();
t1.level = 9;
t2.level = 47;
System.out.println("1:t1.level="+t1.level+" t2.level:"+t2.level);
t1.level = t2.level;
System.out.println("1:t1.level="+t1.level+" t2.level:"+t2.level);
t1.level = 27;
System.out.println("1:t1.level="+t1.level+" t2.level:"+t2.level);
}
}
output:
1:t1.level=9 t2.level:47
1:t1.level=47 t2.level:47
1:t1.level=27 t2.level:47
2.截尾和舍入:
eg1:1.7转换为int时,是1还是2呢。
public class a {
public static void main(String[] args) {
double a = 1.7;
// TODO Auto-generated method stub
double b = 1.3;
System.out.println("(int)a:"+(int)a);
System.out.println("(int)b:"+(int)b);
}
}
output:
(int)a:1
(int)b:1
eg2:所以如果想要进行舍入,就需要round()方法。
public class a {
public static void main(String[] args) {
double a = 1.7;
// TODO Auto-generated method stub
double b = 1.3;
System.out.println("(int)a:"+Math.round(a));
System.out.println("(int)b:"+Math.round(b));
}
}
output:
(int)a:2
(int)b:1