stringclassdemo.java

卡内基梅陇大学的网上教程 ssd3第一单元的源码

package unitOne;
import  java.io.*;  // the PrintWriter class is here
//no need to import String since it's in java.lang

/**
* This class is a demo of class String
*
* @author iCarnegie
* version 1.0.0
*/

public class StringClassDemo {


	private static  PrintWriter  stdOut = new  PrintWriter(System.out, true);

	/**
	 * Main method, show the use of class String
	 *
	 * @param args  not used
	 */
	public static void  main(String[]  args)  {

		String  strHello = new  String("Hello");
		
		// string literal will be replaced by new  String("World")
		String  strWorld = "World";

		// string concatenation prints:  Hello, World
		stdOut.println(strHello + ", " + strWorld);

		// prints the character r
		stdOut.println(strWorld.charAt(2));

		// prints the integer 2 which is the index of the first 'l' in strHello
		stdOut.println(strHello.indexOf('l'));

		// prints the integer 1 which is the index of the start of the string
		// "or" in strWorld
		stdOut.println(strWorld.indexOf("or"));

		// prints the integer 6 which is the index of the first 'o' in the
		// string "HelloWorld" starting from index 5
		stdOut.println((strHello + strWorld).indexOf('o', 5));

		// prints:  "Hello" and "World" are equal in length
		stdOut.print("\"" + strHello + "\" and \"" + strWorld + "\" are ");
		if (strHello.length() != strWorld.length())  {
			stdOut.print("not ");
		}
		stdOut.println("equal in length");

		// reassign strWorld to a new String could have
		// been written: strWorld = "Hello";
		strWorld = new  String("Hello");  

		// nothing is printed here
		// This may be surprising, but remember, since
		// Strings are objects, the == compares the addresses
		// of the objects, not the objects themselves.
		if (strHello == strWorld)  {
			stdOut.println("The strings are equivalent according to ==");
		}

		// the following is what should have been written
		// prints:  The strings are equivalent.
		if (strHello.equals(strWorld))  {
			stdOut.println("The strings are equivalent.");
		}

		// a group of static methods exist to convert from
		// a primitive to a String representation of it
		String  strValues;

		strValues = String.valueOf(5.87);  // strValues is now "5.87"
		strValues = String.valueOf(true);  // strValues is now "true"
		strValues = String.valueOf(18);  // strValues is now "18"

		// concatenation
		stdOut.println(strValues+" , "+5.87 + "" + true + "" + 18);  // prints 5.87true18
	}


}