Tips When Using Component Objects

You can assign objects in the same manner as you assign DATA step variables. However, the object types must match. The first set of code is valid, but the second generates an error.
```
declare hash h();
declare hash t();
t=h;
```
```
declare hash t();
declare javaobj j();
j=t;
```
You cannot declare arrays of objects. The following code would generate an error:
```
declare hash h1();
declare hash h2();
array h h1–h2;
```

You can store a component object in a hash object as data but not as keys.

data _null_;
   declare hash h1();
   declare hash h2();
   
   length key1 key2 $20;

   h1.defineKey('key1');
   h1.defineData('key1', 'h2');
   h1.defineDone();

   key1 = 'abc';
   h2 = _new_ hash();
   h2.defineKey('key2');
   h2.defineDone();

   key2 = 'xyz';
   h2.add();
   h1.add();

   key1 = 'def';
   h2 = _new_ hash();
   h2.defineKey('key2');
   h2.defineDone();

   key1 = 'abc';
   rc = h1.find();
   h2.output(dataset: 'work.h2');
run;

proc print data=work.h2;
run;

The data set WORK.H2 is displayed.

Data Set WORK.H2

You cannot use component objects with comparison operators other than the equal sign (=). If H1 and H2 are hash objects, the following code will generate an error:
```
if h1>h2 then
```
After you declare and instantiate a component object, you cannot assign a scalar value to it. If J is a Java object, the following code will generate an error:
```
j=5;
```
You have to be careful to not delete object references that might still be in use or that have already been deleted by reference. In the following code, the second DELETE statement will generate an error because the original H1 object has already been deleted through the reference to H2. The original H2 can no longer be referenced directly.
```
declare hash h1();
declare hash h2();
declare hash t();
t=h2;
h2=h1;
h2.delete();
t.delete();
```
You cannot use component objects in argument tag syntax. In the following example, using the H2 hash object in the ADD methods will generate an error.
```
declare hash h2();
declare hash h();
h.add(key: h2);
h.add(key: 99, data: h2);
```
The use of a percent character (%) in the first byte of text output by Java to the SAS log is reserved by SAS. If you need to output a % in the first byte of a Java text line, it must be escaped with another percent immediately next to it (%%).
You can have a hash table of hash tables.
A Java object represents an instantiation of a single Java class. A Java object cannot hold anything else. But the Java instance can be arbitrarily complicated just like any Java instance. A Java object can contain references to other Java entities, but they are not considered Java objects.
When SAS is in a locked-down state, the Java object is not available. For more information, see SAS Processing Restrictions for Servers in a Locked-Down State in SAS Language Reference: Concepts.