(Review:) How can you determine what an object of a particular class can do?
The variables and methods of a class will be documented somewhere.
String
With a Java development environment
such as such as Borland JBuilder or Symantec Café
the documentation is on-line
(in the editor, put the cursor over a class name and push F1).
If you got Java from Sun Microsystems, look
on your hard disk,
in someplace like
C:\jdk1.3\docs\index.html.
Here is a short version of the documentation for String
.
// Constructors public String(); public String(String value); // Methods public char charAt(int index); public String concat(String str); public boolean endsWith(String suffix); public boolean equals(Object anObject); public boolean equalsIgnoreCase(String anotherString); public int indexOf(int ch); public int indexOf(String str); public int length(); public boolean startsWith(String prefix); public String substring(int beginIndex, int endIndex); public String toLowerCase(); public String toUpperCase(); public String trim();
The documentation first lists constructors. Then it describes the methods. For example,
public String concat(String str); --+--- --+--- --+-- ----+---- | | | | | | | | | | | +---- says that there must be a | | | String reference parameter | | | | | +----- the name of the method | | | +----- the method returns a reference | to a new String object | +----- anywhere you have a String object, you can use this method