The String Class

• String variables (Slides)
  • Example: HelloWorld.java
  • Example: StringVar.java
  • Example: StringVar3.java
  • Example: StringCat.java
  • Example: StringVar2.java

• Strings and mutation (Slides)
  • Example: StringImmut.java
  • Example: StringAlias2.java

• Inside strings (Slides)
  • Example: StringVowels.java
  • Example: StringWords.java
  • Example: StringAlias.java
  • Example: StringJavas.java
  • More in the SUN documentation.

• Strings and methods (Slides)
  • Example: StringMethod.java

• Command line arguments
  • The formal arguments to the main method receive strings from the command line arguments.
  • When running a program, supply command line arguments after the program name, e.g.,

    prompt> java MyJavaProgram cat 27 'Java is great!' 

    has three command line arguments.
  • Example: MyJavaProgram.java

• StringBuffers (Slides)
  • Example: StringBufferX.java
  • Example: StringBufferMake.java

Exercises

• Are strings primitive or reference data values?

Exam Style Questions

• How many string objects are created in the following code segment:

  System.out.print("Enter a sentence : ");
  mySentence = keyboard.next();
  System.out.println("The original is  : " + mySentence);
  mySentence.toUpperCase();
  System.out.println("The same one is  : " + mySentence);
  mySentence = mySentence.toUpperCase();
  System.out.println("The raised is    : " + mySentence); 

• Write a program that prints its command line parameters on the screen.
• What operator concatenates strings?
• What is the output from the following code segment:

       String one = "aaa";
       String two = "bbb";
       String three;
  
       one = one + one;
       three = two;
       two = three + one;
       System.out.println(one + two + three); 

• Write a method that returns the number of spaces in a string.
• Explain the difference between

  if (aString == anotherString) { 

  and

  if (aString.equals(anotherString)) { 

• What is the critical difference between and String and a StringBuffer?