Data Types Concept

src/coreJava/DataTypes.java

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+package coreJava;
+
+public class DataTypes {
+
+	public static void main(String[] args) {
+
+	//variables
+
+		//int s; //declaration
+		//s=100; //assignment
+
+		int s=100; 	// declaration+assignment
+		System.out.println(s);
+
+		s=200;
+		System.out.println(s);
+
+	/*	
+	// approach1  // if all the variables belongs to different data types
+		int p=1;
+		int o=2;
+		int i=3;
+	*/
+
+	/* approach2 // only if allthe variable are belongs to same data type
+	 	int p,o,i;
+	 	p=1;
+	 	o=2;
+	 	i=3;
+	 */
+
+	// approach3 //only if all the variable are belongs to same data type
+	 	int p=1,o=2,i=3;
+
+	//for meaningful message in print statement we can use concatenation method		
+	 	System.out.println("The Value of p is :"+p);
+		System.out.println("The Value of o is :"+o);
+		System.out.println("The Value of i is :"+i); 
+
+	// in single line we printed all variable values
+	 	System.out.println(p+""+o+""+i+"");
+
+	// in print statement we used join method for each value with ""	
+
+
+//--------------------------------------------------------------------------	
+	// Data types
+
+		// Numeric Data Types
+
+				int a=100, b=200;
+				System.out.println("The Value of a is :"+a);
+				System.out.println("The Value of b is :"+b);
+				System.out.println(a+b);
+				System.out.println("The sum of an and b is : "+(a+b));
+
+				byte by=125;
+				System.out.println(by);
+
+				short sh=32767;
+				System.out.println(sh);
+
+				long l=21212121234443534L; // literal is needed
+				// L should add, it can be lower or uppercase
+				System.out.println(l);
+
+				// Decimal numbers - float, double
+
+				float item_price=15.5f; // literal is needed
+				//f should add, it can be lower or uppercase
+				System.out.println(item_price);
+
+				double dbl=1234.4343412;
+				System.out.println(dbl);
+
+				// characters
+
+				char grade='A'; // single character in single quotes - ''
+				System.out.println(grade);
+
+				String name="Harish"; // String is non-premitive type and multiple characters with double quotes - ""
+				System.out.println(name);
+
+				//char ch='abc'; //invalid
+				//Stirng ch='abc';//invalid
+				//String ch='A';//invalid
+				String ch="A"; //valid
+				System.out.println(ch);
+
+				boolean bl=true; //allows only true or false
+				System.out.println(bl);
+
+				boolean bl1=false;//allows only true or false
+				System.out.println(bl1);
+
+				//boolean bl="true";//invalid
+				//boolean bl="false";//invalid
+
+				//String bl=true;//invalid
+				 String bl2="true";//valid
+
+	//----------------------------------------------------------------------	
+
+				 //difference between variable and const/final
+				 int x=100;
+				 System.out.println(x);
+				x=200;
+				System.out.println(x);
+
+				final int y=300;
+				System.out.println(y);
+				// y=400;// not allowed
+				//System.out.println(y);
+
+				// variables declaration without final keyword we can change the values but wiht final keyword we cnat chaneg the value. in javascript instea dof final, const keyword is used.
+
+				//java is statistically typed programming language
+				//python is dynamically typed programming language
+				//javascript is dynamically typed scripting language
+
+				//Example :
+
+				int q=100;
+				//x="welcome";//it is not allowed in java but in javascript and python it is allowed
+				//in python or javascript we no need to specify the data types explicitly.
+
+				/* 
+				 r=100;
+				 r="welcome";
+				 */ 
+				//it is allowed in dynamically typed programming language - javascript / python
+
+	}
+
+}