The variables and methods of a class will be documented somewhere.
String
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to find documentation for class String.
Search for Java String.
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 );
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 the method requires 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
public will be explained in greater detail in another chapter.
Is the following code correct?
String first = "Red " ; String last = "Rose" ; String name = first.concat( last );
You don't have to know what concat() does (yet);
look at the documentation and see if all the types are correct.