else、else if

中級 Java

Jim White

Java Developer

複数の if

if (score >= 90) {
  System.out.println("Excellent!");  
}

if (score >= 70) {
  System.out.println("Good effort.");  
}

if (score < 70) {
  System.out.println("Keep trying!");  
}

もし score >= 70 なら、Excellent! と Good effort. の両方が出力されます。

➡ if を複数使うと煩雑になります

if - else if - else

int score = 80;

if (score >= 90) { 
  System.out.println("Excellent!");  
} else if (score >= 70) { 
  // Only this code is executed
  System.out.println("Good effort.");  
} else {
  System.out.println("Keep trying!");  
}

Good effort.

int score = 60;

if (score >= 90) {
  System.out.println("Excellent!");  
} else if (score >= 70) { 
  System.out.println("Good effort.");  
} else { // Only this code is executed
  System.out.println("Keep trying!");  
}

Keep trying!

実行されるのは1つのブロックのみ

int score = 95;

if (score >= 90) { // Only this code is executed
  System.out.println("Excellent!");  
} else if (score >= 70) { 
  System.out.println("Good effort.");  
} else {
  System.out.println("Keep trying!");  
}

Excellent!

必要なだけ使えるが、順序に注意

// As many as we want
if (score >= 95) { 
  System.out.println("Excellent job, well done!");  
} else if (score >= 90) { 
  System.out.println("Excellent!");  
}  else if (score >= 80) { 
  System.out.println("Great job.");  
}  else if (score >= 70) { 
  System.out.println("Good effort.");  
} else {
  System.out.println("Keep trying!");  
}

// Be careful with the order
int score = 95;

if (score > 70) { // This code runs
  System.out.println("Good effort.");  
} else if (score >= 90) { 
  // This is also valid
  System.out.println("Excellent!");  
} else {
  System.out.println("Keep trying!");  
}

Good effort.

まとめ

int age = 33;

if (age < 20) {
    System.out.println("You are a teenager");
} else if (age < 30) {
    System.out.println("You are in your twenties");
} else if (age < 40) { // Only this code block will be executed
    System.out.println("You are in your thirties");
} else {
    System.out.println("You are older than 39");
}

You are in your thirties

Ayo berlatih!

中級 Java