3. Essential Java Classes. 1. Strings

Strings

Strings are a sequence of characters.
In the Java strings are

String Length

String palindrome = "А роза упала на лапу Азора";
int

Concatenation and addition

int a = 5;
int b = 3;
String S =

Converting Numbers to Strings

The simplest way:
String s = "" + 6;
Another

Strings Comparing (1 of 3)

String s1 = "hello";
String s2 = "hello";

Strings Comparing (2 of 3)

String s1 = "hello";
String s2 = new

Strings Comparing (3 of 3)

You should use equals method instead of

Some String Methods

indexOf(String subString)
substring(int posBeg, int posEnd)
toUpperCase(), toLowerCase()
trim()
replace(CharSequence targ,

indexOf method

String palindrome = "Niagara. O roar again!";
System.out.println(palindrome.indexOf("roar"));
What will be

substring Method

String palindrome = "Niagara. O roar again!";
System.out.println(palindrome.substring(11, 15));
System.out.println(palindrome.substring(11));
What will

replace Method

String s = "Niagara. O roar again!";
s = s.replace("a", "A");
System.out.println(s);
What

split Method

String palindrome = "Niagara. O roar again!";
String[] txt =

String Methods

See http://docs.oracle.com/javase/7/docs/api/java/lang/String.html for details

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Exercise 3.1.1.

Write a program that computes your initials from your

Exercise 3.1.1.
See 311Initials project for the full text.

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Strings and Arrays

It is impossible to work with strings as with

String Formatting

String s1 = "";
s1 = String.format("a =%1$3d, b =%2$7.2f, b

Format String

The format string consists of static text embedded with format

Format Specifiers

d formats an integer value as a decimal value.
f formats

Examples of Format Specifiers

System.out.format("%1f, %1$+012.10f %n", Math.PI);
Output is 3.141593, +03.1415926536

Application main Method

Every application must contain a main method whose signature

How to Run Application with Arguments in Eclipse

Right click on project

Exercise 3.1.2.

Create a program that will print every other argument

Run Application
java app/E312Arguments one two three a b c d

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JAR Files

The Java Archive (JAR) file format enables you to bundle

Create JAR File in Eclipse

Open workspace with necessary project
Menu item File

Run Application
java -jar ArgumentSkipper.jar one two three a b c d

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String vs StringBuilder

Objects of the String class are immutable.
A new String

StringBuilder Methods (1 of 2)

indexOf(String subString)
substring(int posBeg, int posEnd)
length()
The

StringBuilder Methods (2 of 2)

append(type arg) - appends the argument to

append Method

StringBuilder s1 = new StringBuilder("Hello");
s1.append(" world!");
System.out.println(s1);
What will be the output?

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insert Method

StringBuilder s1 = new StringBuilder("Niagara again!");
s1.insert(7, ". O roar");
System.out.println(s1);
What will

replace Method

StringBuilder s1 = new StringBuilder("Niagara. O roar again!");
s1.replace(7, 16, "

reverse Method

StringBuilder s1 = new StringBuilder("Niagara. O roar again!");
s1.reverse();
System.out.println(s1);
What will be

Exercise 3.1.3.

A palindrome is a text phrase that spells the same

Home Exercise 3.1.4.

Create a generateString method that gets an integer