Java · Theory

Java 8 forEach() method

Theory

239/270

Java 8 forEach() method

8 forEach() method is modern Java (5/8 toolkit). Lambdas are short functions: (n) -> print. They implement a functional interface (one abstract method). Streams let you filter/map/collect a list without a manual loop.

For 8 forEach() method: generics keep types safe: List<String>. Autoboxing turns int into Integer when needed. varargs is String... args. Optional avoids some null checks — don’t overuse it.

Keep 8 forEach() method small. Don’t dump business logic inside forEach. Know one tiny example you can write from memory.

Let's take this on the board with one tiny Main class — no extra files. Java 8 forEach() method — output: 10 then 20 then 30. for-each walks the array — no index variable. Start from main, go line by line, and stop at each print. That output is the proof for 8 forEach() method.

Exam tip

Say: for-each is for reading; classic for when index matters.

Example

// For-Each Loop
public class Main {
  public static void main(String[] args) {
    int[] nums = {10, 20, 30};
    for (int x : nums) {
      System.out.println(x);
    }
  }
}

Java 8 forEach() method — output: 10 then 20 then 30. for-each walks the array — no index variable.

Short notes

Def8 forEach() method is part of modern Java (generics / Java 8 style).
Rule8 forEach() method — lambda = (args) -> body on a functional interface.
Use8 forEach() method — streams filter/map/collect. Generics = List<String>.
Trap8 forEach() method — huge logic inside lambdas, or forgetting generics.

Java · Theory

Java 8 forEach() method

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Theory

239/270

Java 8 forEach() method

For 8 forEach() method: generics keep types safe: List<String>. Autoboxing turns int into Integer when needed. varargs is String... args. Optional avoids some null checks — don’t overuse it.

Keep 8 forEach() method small. Don’t dump business logic inside forEach. Know one tiny example you can write from memory.

Exam tip

Say: for-each is for reading; classic for when index matters.

Example

// For-Each Loop
public class Main {
  public static void main(String[] args) {
    int[] nums = {10, 20, 30};
    for (int x : nums) {
      System.out.println(x);
    }
  }
}

Java 8 forEach() method — output: 10 then 20 then 30. for-each walks the array — no index variable.

Short notes

Def8 forEach() method is part of modern Java (generics / Java 8 style).
Rule8 forEach() method — lambda = (args) -> body on a functional interface.
Use8 forEach() method — streams filter/map/collect. Generics = List<String>.
Trap8 forEach() method — huge logic inside lambdas, or forgetting generics.

Java 8 forEach() method

Example

Short notes

Questions

Java 8 forEach() method

Example

Short notes

Questions