How to Convert a Primitive Type Value to a String

// Use String.valueOf()
String s = String.valueOf(true); // true
s = String.valueOf('a'); // a
s = String.valueOf((short)111); // 111
s = String.valueOf(111); // 111
s = String.valueOf(111L); // 111
s = String.valueOf(1.11F); // 1.11
s = String.valueOf(1.11D); // 1.11

How to Convert a String to Upper or Lower Case

// Convert to upper case
String upper = “abc”.toUpperCase(); // ABC

// Convert to lower case
String lower = “ABC”.toLowerCase(); // abc

How to Search a String for a Character or a Substring

String string = "Java Java";
// First occurrence of a character ‘a’
int index = string.indexOf('a'); // 1

// First occurrence of a sting “dam”
index = string.indexOf("ava"); // 1

How to Get a Substring from a String

int start = 1;
int end = 3;
String substr = "Java".substring(start, end); // av

How to Construct a String

StringBuffer buf = new StringBuffer("Hi");

// Append
buf.append(" Welcome");
buf.append(“ To Java”);

// Convert to string
String s = buf.toString(); // Hi Welcome To Java

How to Compare Strings

String s1 = "a";
String s2 = "A";

// Check if identical
boolean b = s1.equals(s2); // false

// Check if identical ignoring case
b = s1.equalsIgnoreCase(s2); // true

StringBuffer sbuf = new StringBuffer("a");
b = s1.contentEquals(sbuf); // true

How to Construct a String From StringBuffer

StringBuffer buf = new StringBuffer("Hi");
// Append
buf.append(" Welcome");
// Convert StringBuffer to string
String s = buf.toString();

How to Get the Package of a Class

Class cls = java.lang.String.class;
Package packageOfClass = cls.getPackage();
String packageName = packageOfClass.getName(); // java.lang

How to List the Interfaces That a Class Implements

Class cls = java.lang.String.class;
Class[] interfaces = cls.getInterfaces();

How to Get the Superclass of an Object

Object o = new String();
Class superClass = o.getClass().getSuperclass(); // java.lang.Object

How to Determine If a Class Object Represents a Class or Interface

Class cls = java.lang.String.class;
boolean isClass = cls.isInterface(); // false

cls = java.lang.Cloneable.class;
isClass = cls.isInterface(); // true

How to Get the Name of a Class Object

Class cls = java.lang.String.class;
String name = cls.getName();

How to Get an Object of the Class

There are three ways to retrieve a class object.

1) Class cls = object.getClass();

2)
try {

cls = Class.forName("java.lang.String");

} catch (ClassNotFoundException e) {

}

3) cls = java.lang.String.class;