String Manipulation

char initial = 'p';

Note the single quote. Characters take less time to compare than Strings.

hmmm. Consider the java.lang.Character class . Why is this interesting?

You can see the API for java.lang.Strings and java.lang.StringBuffer .
Read These. Discuss use of static (e.g. valueOf)

Do these need to be imported when used in code?

Strings are immutable. What does this mean?

Because of this, old programmers like to use StringBuffer. Here is an example:

• StringDemo and code seen below
  import java.awt.*; import java.applet.*; import java.util.*; import java.awt.event.*; public class StringDemo extends Applet implements ActionListener { private TextField string1Field, string2Field; private TextField resultField; Label string1Label, string2Label, resultLabel; Button goButton; public void init() { string1Label = new Label("Type string1: "); string2Label = new Label("Type string2: "); resultLabel = new Label("result is: "); goButton = new Button("do it"); string1Field = new TextField(20); string2Field = new TextField(20); resultField = new TextField(40); resultField.setEditable(false); add(string1Label); add(string1Field); add(string2Label); add(string2Field); add(goButton); goButton.addActionListener(this); add(resultLabel); add(resultField); } public void actionPerformed(ActionEvent event) { String result =""; if (event.getSource() == goButton) { String string1 = string1Field.getText(); String string2 = string2Field.getText(); // string example - enter string1 and string2 //.... insert your code here if(string1.equals(string2)) result="They are equal."; else result="They are not equal."; // end of example resultField.setText(result); } } } Because of no LayoutManager, where the components are placed depends on the .html page applet tag size (ie, how much length before "flow")

  Other methods:

  • equals
  • equalsIgnoreCase
  • compareTo (like alphabetical order) note IN is before at
    Look at API to see what returns

  Strings are immutable, but you can make new strings:

  string1 = "Mississippi".replace('i','a');

  Other methods:

  • substring(int beginIndex) and substring(int beginIndex, int endIndex)
  • toLowerCase()
  • trim() ...cool. Returns a copy of the string, with leading and trailing whitespace omitted.
  • length()

• AskFrasier applet and code

is compiled to the equivalent of:

     x = new StringBuffer().append("a").append(4).append("c")
                           .toString()
 

The principal operations on a StringBuffer are the append and insert methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string buffer. The append method always adds these characters at the end of the buffer; the insert method adds the characters at a specified point.

For example, if z refers to a string buffer object whose current contents are "start", then the method call z.append("le") would cause the string buffer to contain "startle", whereas z.insert(4, "le") would alter the string buffer to contain "starlet".

Every string buffer has a capacity. As long as the length of the character sequence contained in the string buffer does not exceed the capacity, it is not necessary to allocate a new internal buffer array. If the internal buffer overflows, it is automatically made larger.