How to construct an Integer:

• public Integer(int value)
• public Integer(String s)

Note: this string must be composed of numeric characters
The code example is as follows:

public class IntegerDemo {
	public static void main(String[] args) {
		//Mode 1
		int i = 100;
		Integer i1 = new Integer(i);
		System.out.println("i1:"+i1);
		
		//Mode 2
		String s = "100";
		//NumberFormatException
		//String s = "abc";
		
		Integer ii = new Integer(s);
		System.out.println("ii:"+ii);
	}
}

Operation result:
i1:100
ii:100

Conversion between int type and String type:
The methods of int - > string are as follows:

• Method 1: String splicing
• Method 2: String.valueOf() method of String
• Mode 3: int > integer > string
• Mode 4: toString method of Integer

The demo code is as follows:

public class IntegerDemo {
	public static void main(String[] args) {
		//int	---	String
		int number = 100;
		//Method 1 string splicing
		String s1 = "" + number;
		System.out.println("s1:"+s1);
		//Mode two
		String s2 = String.valueOf(number);
		System.out.println("s2:"+s2);
		//Mode three
		//int	--	Integer	--	String
		Integer i = new Integer(number);
		String s3 = i.toString();
		System.out.println("s3:"+s3);
		//Mode four
		//public static String toString(int i)
		String s4 = Integer.toString(number);
		System.out.println("s4:"+s4);
		System.out.println("--------------------");
	}
}

Operation result:
s1:100
s2:100
s3:100
s4:100

String - > int can be used in the following ways:

• Method 1: String > integer > int, and then public int intValue()
• Method 2: public static int parseInt(String s)

The sample code is as follows:

public class IntegerDemo {
	public static void main(String[] args) {
	//String	--	int
		String s = "100";
		//One way
		//String	--	Integer	--	int
		Integer ii = new Integer(s);
		//public int intValue()
		int x = ii.intValue();
		System.out.println("x:"+x);
		
		//Mode two
		//public static int parseInt(String s)
		int y =	Integer.parseInt(s);
		System.out.println("y:"+y);
	}
}

Operation result:
x:100
y:100