Java中参数传递是传值还是传引用呢？很多人遇到这个问题都会马上给你抛出这个例子：
class Entry{
Integer value; public Entry(Integer v){ this.value = v;
}
@Override public String toString() { return "Entry[value=" + value + "]";
}
}public class CallByDemo{ public static void swap(int a,int b){ int temp = a;
a = b;
b = a;
} public static void swap(Entry e1,Entry e2){
Integer temp = e1.value;
e1.value = e2.value;
e2.value = temp;
} public static void main(String[] args) { int a = 1; int b = 2;
System.out.println("before:a="+a+",b="+b);
swap(a,b);
System.out.println("after :a="+a+",b="+b);
Entry e1 = new Entry(new Integer(1000));
Entry e2 = new Entry(new Integer(2000));
System.out.println("before:e1="+e1+"e2="+e2);
swap(e1,e2);
System.out.println("after :e1
