Conditional

자바의 조건문에 대해 정리하였습니다.

 

 

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< Introduction >

To make decisions based on circumstances.
This means To check a specific condition(s) and perform a task based on the condition(s)

 

 

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< If Statement >

< Syntax >

if (condition) {
	// code block
}

• Condition evaluates to true, block runs.
• Condition evaluates to false, block won't run.
  

Note: Conditional statements do not end in a semicolon.

 

 

Example)

if (number > 12) {
  System.out.println("Number is greater than 12");
}

 

+. If a conditional is brief we can omit the curly braces entirely:

if (true) System.out.println("Brief Sentence");

 

 

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< If-Else Statement >

< Syntax >

if (condition) {
  // code block-1
} else {
  // code block-2
}

• Condition evaluates to true, code block-1 runs.
• Condition evaluates to false, code block-2 runs.
  

 

 

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< If-Else if Statement >

< Syntax >

if (condition) {
  // code block-1
} else if (condition) {
  // code block-2
} else if (condition) {
  // code block-3
} ...

• The first condition to evaluate to true will have that code block run.
• Only one of the code blocks will run.
  

 

Example)

if (Number > 10) {
  System.out.println("Number is greater than 10");
} else if (Number > 20) {
  System.out.println("Number is greater than 20");
} else if (Number > 30) {
  System.out.println("Number is greater than 30");
} else {
  System.out.println("Input Number");
}

 

 

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< Nested Conditional Statements >

We can create more complex conditional structures by creating nested coditional statements.

 

Example)

int temp = 45;
boolean raining = true;
 
if (temp < 60) {
  System.out.println("Wear a jacket!");
  if (raining == true) {
    System.out.println("Bring your umbrella.");
  } else {
    System.out.println("Leave your umbrella home.");
  }
}

 

 

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< Switch Statement >

An else if 's another version. It's easier to read and write!

 

< Syntax >

switch (expression) {
  case value1:
    // code block-1
    break;
  case value2:
    // code block-2
    break;
  
  //...
  default:
    // default code block
}

• If the expression matches the specified value, that case's code block will run.
• The break keyword tells the computer to exit the block and not execute any more code.
  Note : Without break keywords, every subsequent case will run regardless of wheter or not it matches!
  
• If none of the cases are true, then the code in the default statement will run.

 

Example)

String course = "Biology";
 
switch (course) {
  case "Algebra": 
    // Enroll in Algebra
  case "Biology": 
    // Enroll in Biology
  case "History": 
    // Enroll in History
  case "Theatre":
    // Enroll in Theatre
  default:
    System.out.println("Course not found");
}