The article directories

• Basic data type conversion
• • 1. Automatic type conversion
  • 2. Automatic type conversion notes and details
  • 3. Cast type
  • 4. Cast details
  • 5. Basic data type conversion – Exercises

Basic data type conversion

1. Automatic type conversion

	// demonstrate automatic conversion
	int num = 'a';//ok char -> int
	double d1 = 80; //ok int -> double
	System.out.println(num);/ / 97
	System.out.println(d1);/ / 80.0
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2. Automatic type conversion notes and details

	// Detail 1: When multiple types of data are mixed,
	// The system first automatically converts all data to the data type with the largest capacity, and then performs the calculation
	int n1 = 10; //ok
	//float d1 = n1 + 1.1; // error n1 + 1.1 => Result type double
	//double d1 = n1 + 1.1; N1 + 1.1 => The result type is double
	float d1 = n1 + 1.1 F;N1 + 1.1 => The result type is float
	
	// Detail 2: When we assign a high precision data type to a low precision data type,
	// An error is reported, otherwise an automatic type conversion is performed.
	//
	/ / int n2 = 1.1; // double -> int
	
	// Detail 3: (byte, short) and char do not automatically convert to each other
	// When assigning a specific number to byte, (1) first checks whether the number is in byte range, if so
	byte b1 = 10; / / to - 128-127
	// int n2 = 1; / / n2 is int
	// byte b2 = n2; // Error, cause: If a variable is assigned, determine the type
	// 
	// char c1 = b1; // Error because byte cannot be automatically converted to char
	// 
	// 
	
	// Detail 4: byte, short, char these three can be computed, and are first converted to int when computed
	
	byte b2 = 1;
	byte b3 = 2;
	short s1 = 1;
	//short s2 = b2 + s1; B2 + s1 => int
	int s2 = b2 + s1;B2 + s1 => int
	
	//byte b4 = b2 + b3; // Error: b2 + b3 => int
	//
	
	// Boolean does not participate in the conversion
	boolean pass = true;
	//int num100 = pass; // Boolean does not participate in automatic conversion of types
	
	// Automatic promotion principle: The type of the result of an expression is automatically promoted to the largest type of the operand
	// Look at a problem
	
	byte b4 = 1;
	short s3 = 100;
	int num200 = 1;
	float num300 = 1.1 F;
	
	double num500 = b4 + s3 + num200 + num300; //float -> double
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3. Cast type

	// demonstrate casting
	int n1 = (int)1.9;
	System.out.println("n1=" + n1);//1, resulting in accuracy loss
	
	int n2 = 2000;
	byte b1 = (byte)n2;
	System.out.println("b1=" + b1);//-48, causing a data overflow
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4. Cast details

• 10 near the parentheses is converted to an int, multiplied by 3.5 to a double, resulting in a double and not an int

	// demonstrate casting
	// Strong conversions are valid only for the most recent operand. Parentheses are often used to raise the priority
	/ / int x = (int) 10 * 3.5 + 6 * 1.5; Error: double -> int
	int x = (int) (10*3.5+6*1.5);/ / 44.0 > 44 (int)
	System.out.println(x);/ / 44
	
	
	char c1 = 100; //ok
	int m = 100; //ok
	//char c2 = m; / / error
	char c3 = (char)m; //ok
	System.out.println(c3);//100 corresponds to the d character
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5. Basic data type conversion – Exercises