java oop : wrapper class

JavaOOP/src/Java33.java

@@ -1,5 +1,8 @@
 import kr.study.IntArray;
 
+import java.util.ArrayList;
+import java.util.List;
+
 public class Java33 {
     public static void main(String[] args) {
 

JavaOOP/src/Java34.java

@@ -0,0 +1,64 @@
+public class Java34 {
+    public static void main(String[] args) {
+
+        int a = 1; // 기본자료형
+        Integer b = new Integer(1); // 객체자료형
+
+        System.out.println(a);
+        System.out.println(b.intValue()); // 1
+        System.out.println(b.toString()); // "1"
+
+        System.out.println("=======================");
+
+        int c = new Integer(1); // unboxing
+        Integer d = 1; // boxing
+
+        System.out.println(c);
+        System.out.println(d.intValue()); // 1
+        System.out.println(d.toString()); // "1"
+
+        System.out.println("=======================");
+
+        Object[] obj = new Object[3];
+        obj[0] = new Integer(1);
+        obj[1] = new Integer(2);
+        obj[2] = new Integer(3);
+
+        System.out.println(obj[0].toString());
+        System.out.println(obj[1].toString());
+        System.out.println(obj[2].toString());
+
+        System.out.println("=======================");
+
+        Object[] obj2 = new Object[3];
+        obj2[0] = 1;
+        obj2[1] = 2;
+        obj2[2] = 3;
+
+        System.out.println(obj2[0].toString());
+        System.out.println(obj2[1].toString());
+        System.out.println(obj2[2].toString());
+
+        System.out.println("=======================");
+
+        // "100" + "100" = 200
+        String x = "100";
+        String y = "100";
+        System.out.println(x + y); // "100100"
+
+        System.out.println("=======================");
+
+        int i = Integer.parseInt(x);
+        int j = Integer.parseInt(y);
+
+        System.out.println(i + j); // 200
+
+        System.out.println("=======================");
+
+        // 100 + 100 = "100100"
+        String v1 = String.valueOf(i);
+        String v2 = String.valueOf(j);
+
+        System.out.println(v1 + v2);
+    }
+}