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JAVA EXAMPLE PAGE 2
Java Examples - String Reverse
Problem Description:
How to reverse a String?
Solution:
Following example shows how to reverse a String after taking it from command line argument .The program buffers the input String using StringBuffer(String string) method, reverse the buffer and then converts the buffer into a String with the help of toString() method.
public class StringReverseExample{
public static void main(String[] args){
String string="abcdef";
String reverse = new StringBuffer(string).
reverse().toString();
System.out.println("\nString before reverse:
"+string);
System.out.println("String after reverse:
"+reverse);
}
}
Result:
The above code sample will produce the following result.
String before reverse:abcdef
String after reverse:fedcba
Java Examples - Search in a String
Problem Description:
How to search a word inside a string ?
Solution:
This example shows how we can search a word within a String object using indexOf() method which returns a position index of a word within the string if found. Otherwise it returns -1.
public class SearchStringEmp{
public static void main(String[] args) {
String strOrig = "Hello readers";
int intIndex = strOrig.indexOf("Hello");
if(intIndex == - 1){
System.out.println("Hello not found");
}else{
System.out.println("Found Hello at index "
+ intIndex);
}
}
}
Result:
The above code sample will produce the following result.
Found Hello at index 0
Java Examples - Spliting a String
Problem Description:
How to split a string into a number of substrings ?
Solution:
Following example splits a string into a number of substrings with the help of str split(string) method and then prints the substrings.
public class JavaStringSplitEmp{
public static void main(String args[]){
String str = "jan-feb-march";
String[] temp;
String delimeter = "-";
temp = str.split(delimeter);
for(int i =0; i < temp.length ; i++){
System.out.println(temp[i]);
System.out.println("");
str = "jan.feb.march";
delimeter = "\\.";
temp = str.split(delimeter);
}
for(int i =0; i < temp.length ; i++){
System.out.println(temp[i]);
System.out.println("");
temp = str.split(delimeter,2);
for(int j =0; j < temp.length ; j++){
System.out.println(temp[j]);
}
}
}
}
Result:
The above code sample will produce the following result.
jan
feb
march
jan
jan
feb.march
feb.march
jan
feb.march
Java Examples - Converting into uppercase
Problem Description:
How to convert a string totally into upper case?
Solution:
Following example changes the case of a string to upper case by using String toUpperCase() method.
public class StringToUpperCaseEmp {
public static void main(String[] args) {
String str = "string abc touppercase ";
String strUpper = str.toUpperCase();
System.out.println("Original String: " + str);
System.out.println("String changed to upper case: "
+ strUpper);
}
}
Result:
The above code sample will produce the following result.
Original String: string abc touppercase
String changed to upper case: STRING ABC TOUPPERCASE
Java Examples - String optimization
Problem Description:
How to optimize string creation ?
Solution:
Following example optimizes string creation by using String.intern() method.
public class StringOptimization{
public static void main(String[] args){
String variables[] = new String[50000];
for( int i=0;i <50000;i++){
variables[i] = "s"+i;
}
long startTime0 = System.currentTimeMillis();
for(int i=0;i<50000;i++){
variables[i] = "hello";
}
long endTime0 = System.currentTimeMillis();
System.out.println("Creation time"
+ " of String literals : "+ (endTime0 - startTime0)
+ " ms" );
long startTime1 = System.currentTimeMillis();
for(int i=0;i<50000;i++){
variables[i] = new String("hello");
}
long endTime1 = System.currentTimeMillis();
System.out.println("Creation time of"
+ " String objects with 'new' key word : "
+ (endTime1 - startTime1)
+ " ms");
long startTime2 = System.currentTimeMillis();
for(int i=0;i<50000;i++){
variables[i] = new String("hello");
variables[i] = variables[i].intern();
}
long endTime2 = System.currentTimeMillis();
System.out.println("Creation time of"
+ " String objects with intern(): "
+ (endTime2 - startTime2)
+ " ms");
}
}
Result:
The above code sample will produce the following result.The result may vary.
Creation time of String literals : 0 ms
Creation time of String objects with 'new' key word : 31 ms
Creation time of String objects with intern(): 16 ms
Java Examples - Concatenate Strings
Problem Description:
How to optimize string concatenation ?
Solution:
Following example shows performance of concatenation by using "+" operator and StringBuffer.append() method.
public class StringConcatenate{
public static void main(String[] args){
long startTime = System.currentTimeMillis();
for(int i=0;i<5000;i++){
String result = "This is"
+ "testing the"
+ "difference"+ "between"
+ "String"+ "and"+ "StringBuffer";
}
long endTime = System.currentTimeMillis();
System.out.println("Time taken for string"
+ "concatenation using + operator : "
+ (endTime - startTime)+ " ms");
long startTime1 = System.currentTimeMillis();
for(int i=0;i<5000;i++){
StringBuffer result = new StringBuffer();
result.append("This is");
result.append("testing the");
result.append("difference");
result.append("between");
result.append("String");
result.append("and");
result.append("StringBuffer");
}
long endTime1 = System.currentTimeMillis();
System.out.println("Time taken for String concatenation"
+ "using StringBuffer : "
+ (endTime1 - startTime1)+ " ms");
}
}
Result:
The above code sample will produce the following result.The result may vary.
Time taken for stringconcatenation using + operator : 0 ms
Time taken for String concatenationusing StringBuffer : 22 ms
Java Examples - String unicode
Problem Description:
How to determine the Unicode code point in string ?
Solution:
This example shows you how to use codePointBefore() method to return the character (Unicode code point) before the specified index.
public class StringUniCode{
public static void main(String[] args){
String test_string="Welcome to TutorialsPoint";
System.out.println("String under test is = "+test_string);
System.out.println("Unicode code point at"
+" position 5 in the string is = "
+ test_string.codePointBefore(5));
}
}
Result:
The above code sample will produce the following result.
String under test is = Welcome to TutorialsPoint
Unicode code point at position 5 in the string is =111
Java Examples - String buffering
Problem Description:
How to buffer strings ?
Solution:
Following example buffers strings and flushes it by using emit() method.
public class StringBuffer{
public static void main(String[] args) {
countTo_N_Improved();
}
private final static int MAX_LENGTH=30;
private static String buffer = "";
private static void emit(String nextChunk) {
if(buffer.length() + nextChunk.length() > MAX_LENGTH) {
System.out.println(buffer);
buffer = "";
}
buffer += nextChunk;
}
private static final int N=100;
private static void countTo_N_Improved() {
for (int count=2; count7lt;=N; count=count+2) {
emit(" " + count);
}
}
}
Result:
The above code sample will produce the following result.
2 4 6 8 10 12 14 16 18 20 22
24 26 28 30 32 34 36 38 40 42
44 46 48 50 52 54 56 58 60 62
64 66 68 70 72 74 76 78 80 82
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