Java build class from string

Class StringBuilder

A mutable sequence of characters. This class provides an API compatible with StringBuffer , but with no guarantee of synchronization. This class is designed for use as a drop-in replacement for StringBuffer in places where the string buffer was being used by a single thread (as is generally the case). Where possible, it is recommended that this class be used in preference to StringBuffer as it will be faster under most implementations.

The principal operations on a StringBuilder are the append and insert methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string builder. The append method always adds these characters at the end of the builder; the insert method adds the characters at a specified point.

For example, if z refers to a string builder object whose current contents are » start «, then the method call z.append(«le») would cause the string builder to contain » startle «, whereas z.insert(4, «le») would alter the string builder to contain » starlet «.

In general, if sb refers to an instance of a StringBuilder , then sb.append(x) has the same effect as sb.insert(sb.length(), x) .

Every string builder has a capacity. As long as the length of the character sequence contained in the string builder does not exceed the capacity, it is not necessary to allocate a new internal buffer. If the internal buffer overflows, it is automatically made larger.

Instances of StringBuilder are not safe for use by multiple threads. If such synchronization is required then it is recommended that StringBuffer be used.

Unless otherwise noted, passing a null argument to a constructor or method in this class will cause a NullPointerException to be thrown.

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Java build class from string

Java String to Class object Example

Let’s see the simple code to convert String to Class object in java using Class.forName() method. The Class.forName() method returns the instance of Class class which can be used to get the metadata of any class.

Class name: java.lang.String Super class name: java.lang.Object

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How to Convert String to Object in Java

The Object is the super class of all classes. So you can assign a string to Object directly. There are two methods to convert String to Object.

Using Assignment Operator

You can convert String to Object by using the assignment operator. An assignment operator assigns the string into the reference variable of the Object class.

In the following example, we have taken a variable str of type String and initialized “book” into it. An Object is a super class of all classes. obj is a reference variable of the class Object that stores the string str as an object. The println statement prints the object that contains a string.

public class StringToObjectExample < public static void main(String args[]) < String str="book"; Object obj=str; System.out.println(obj); >>

Using Class.forName() method

There is another method Class.forName() to convert String to Object. It belongs to java.lang package. It creates an instance of java.lang.Class and forces the class loader to load this class, and execute code in its static block. The Class.forName() method returns the Class object associated with the class or interfaces with the specified string.

In the following example, getName() is the method of java.lang.reflect.Method class. It returns the method name as a string.

The java.lang.Class class has a method getSuperclass(). It is used to retrieve the direct super class. It returns a Class object representing the super class of the Class Object on which the method is called. If the method is called on the object class, then it returns null.

The first println statement prints the class name and the second println statement prints the super class name of the class java.lang.String.

We should use either try-catch block or write throws Exception just after the main method because it throws ClassNotFoundException.

public class StringToObjectExample2 < public static void main(String args[])throws Exception < Class c=Class.forName("java.lang.String"); System.out.println("class name: "+c.getName()); System.out.println("super class name: "+c.getSuperclass().getName()); >>

class name: java.lang.String super class name: java.lang.Object

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How to Convert String to Object in Java

We are going to start with the Conversion of String to Object in Java with its approach and programming, before that let us look into both String and Object and what do they mean?

In computer programming, a string is a sequence of characters that is used either as a constant or as a variable . The latter may allow for the mutation of its elements and the modification of their length, or it may be fixed (after creation). In computing, a string is a data type that is frequently implemented as an array of bytes (or words) that stores a succession of items, most commonly characters, using some character encoding.

A Java object is a member of a Java class (also known as an instance). There is an identity, a behaviour, and a state for each item. Fields (variables) hold an object’s state, whereas methods (functions) exhibit the object’s action. Templates, often known as classes, are used to build objects at runtime.

What’s the Approach?

• Create a Scanner class object using Scanner sc=new Scanner (System.in);

• Accept the user’s input and store it in a string variable named str.

Java Program to Convert String to Object:

/* * TechDecode Tutorials * * How to Convert String to Object * */ import java.util.*; public class String_To_Object < public static void main(String args[]) < //Creating Scanner Object Scanner sc=new Scanner (System.in); //Accepting user input String str=sc.nextLine(); //Converting Object obj=str; System.out.println("String converted to Object is: "+obj); >>

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