Question

Java Homework Problems:

4.

• Examine AddImport.java.

– Perform the following:

– Replace the fully qualified name to access the Jlabel

component with an import statement.

– To import classes from the util package, replace multiple

import statements with a single import statement.

/*

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* and open the template in the editor.

*/

import java.util.Calendar;

import java.util.Date;

public class AddImport {

    public static void main(String args[]) {

        javax.swing.JLabel label = new javax.swing.JLabel("hello");

    }

}

===========================================================

5.

Exercise 1

• Examine ShoppingCart.java.

– Perform the following:

– Use the indexOf method to get the index for the space character (" ") within custName. Assign it to spaceIdx.

– Use the substring method and spaceIdx to get the first name portion of custName. Assign it to firstName and print firstName.

public class ShoppingCart {

    public static void main (String[] args){

        String custName = "Steve Smith";

        String firstName;

        int spaceIdx;

       

        // Get the index of the space character (" ") in custName.

        // Use the substring method parse out the first name and print it.

    }

   

}

Exercise 2

Examine NameMaker.java.

• Perform the following:

– Declare String variables: firstName, middleName, lastName, and fullName

– Prompt users to enter their first, middle, and last names and read the names from the keyboard.

– Set and display the fullName as firstName+a blank char+middleName+a blank char+lastName.

public class NameMaker {

   

    public static void main(String args[])

    {

       

    }

   

}

Exercise 2

• Which do you think is preferable for this scenario?

• That is, the string concatenation operator or the concat() method?

Answer 1

AddImport.java

//To import classes from the util package, replace multiple //import statements with a single import statement. import java.util.*; //import all swing package import javax.swing.*; import java.awt.event.*; import java.awt.*; public class AddImport { public static void main(String args[]) {    //JFrame    JFrame f=new JFrame();       //JLabel    JLabel label = new JLabel("hello");       //JPanel    JPanel p = new JPanel();       //add JLabel To Panel    p.add(label);       //add JPanel to JFrame    f.add(p);    // set the size of frame f.setSize(300, 300);    //To show JFrame setVisible(true) f.setVisible(true); } }

Output

5. Exercise 1

ShoppingCart.java

public class ShoppingCart { public static void main (String[] args){    String custName = "Steve Smith"; String firstName; int spaceIdx; // Get the index of the space character (" ") in custName. spaceIdx = custName.indexOf(" "); System.out.println("Index of space character (\" \") is : " + spaceIdx + "\n");    // Use the substring method parse out the first name and print it. firstName = custName.substring(0,spaceIdx); System.out.println("First Name is : " + firstName); } }

Output

Exercise 2

NameMaker.java

/ //To import classes from the util package import java.util.*; public class NameMaker {    public static void main(String args[]){           String firstName, middleName, lastName;               // Declare the object and initialize with // predefined standard input object        Scanner reader = new Scanner(System.in);        System.out.println("Enter a firstName: ");        // String input        firstName = reader.nextLine();        System.out.println("Enter a middleName: ");        // String input        middleName = reader.nextLine();               System.out.println("Enter a middleName: ");        // String input        lastName = reader.nextLine();        //Close your scanner        reader.close();               //Concat all three first mid and lastName as        String fullName = firstName + " " + middleName + " " + lastName ;        System.out.println("Full Name is : "+ fullName + )" using + operator");               //Using Concat method        String fullName2=(new StringBuilder()).append(firstName).append(" ").append(middleName).append(" ").append(lastName).toString();        System.out.println("Full Name is :("+ fullName2 + ") using concat method");    }   }

Output

EXERCISE 2

As while using the concatenate + operator you can concatenate A string with any data type.

like you can concat numbers with strings

example: String numberOfBats = 10 + " Bats";

OUTPUT here will be: 10 Bats

But a concatenate method could only be able to concatenate strings (i.e you can't concat strings with numbers etc.)

As in this question, All three user inputs are Strings. you can easily use either concat using append or use + operator without using the concat method.

Here I will prefer the + operator method.