staticでクラス全体で共有する変数をもたせて、コンスタラクタでカウントすればいい
public class Test_iga {
int num ;
static int counter = 0;//クラスの数を数える
static int getCounter(){
return counter;
}
//Constucter
Test_iga() {
int num = counter;
System.out.println("counter in Constructer:" + counter);
counter++;
}
public static void main(String[] args) {
System.out.println("o1.num---------------------");
Test_iga o1 = new Test_iga();
System.out.println("o1.num"+o1.num);
System.out.println("o1.counter"+o1.counter);
System.out.println("getCounter()" + getCounter());
System.out.println("o2.num---------------------");
System.out.println("o2.num");
Test_iga o2 = new Test_iga();
System.out.println("o2.num"+o2.num);
System.out.println("o2.counter"+o2.counter);
System.out.println("getCounter()" + getCounter());
System.out.println("o3.num---------------------");
System.out.println("o3.num");
Test_iga o3 = new Test_iga();
System.out.println("o3.num"+o3.num);
System.out.println("o3.counter"+o3.counter);
System.out.println("getCounter()" + getCounter());
}
}
java Test_iga
o1.num---------------------
counter in Constructer:0
o1.num0
o1.counter1
getCounter()1
o2.num---------------------
o2.num
counter in Constructer:1
o2.num0
o2.counter2
getCounter()2
o3.num---------------------
o3.num
counter in Constructer:2
o3.num0
o3.counter3
getCounter()3
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