Java 8: Formatting lambda with newlines and indentation

In Eclipse, for the single-line statements:

In your project or global preferences, go to Java -> Code Style -> Formatter -> Edit -> Line Wrapping -> Function Calls -> Qualified Invocations, set Wrap all elements, except first if not necessary and tick Force split, even if line shorter than maximum line width.

Eclipse (Mars) has an option for lambda expressions formatter.

Go to Window > Preferences > Java > Code Style > Formatter

Click the Edit button, go to the Braces Tag and set the Lambda Body to Next Line Indented

Another option is update these properties into your project settings. (yourWorkspace > yourProject > .settings > org.eclipse.jdt.core.prefs)

org.eclipse.jdt.core.formatter.insert_space_before_lambda_arrow=insert
org.eclipse.jdt.core.formatter.brace_position_for_lambda_body=next_line_shifted

Out of the box IntelliJ 13 will probably work for you.

If I write it this way:

// Mulit-Line Statement
String[] ppl = new String[] { "Karen (F)", "Kevin (M)", "Lee (M)", "Joan (F)", "Des (M)", "Rick (M)" };
List<String> strings = Arrays.stream(ppl)
        .filter(
                (x) ->
                {
                    return x.contains("(M)");
                }
        ).collect(Collectors.toList());
strings.stream().forEach(System.out::println);

And then apply the auto formatter (no changes):

// Mulit-Line Statement
String[] ppl = new String[]{"Karen (F)", "Kevin (M)", "Lee (M)", "Joan (F)", "Des (M)", "Rick (M)"};
List<String> strings = Arrays.stream(ppl)
        .filter(
                (x) ->
                {
                    return x.contains("(M)");
                }
        ).collect(Collectors.toList());
strings.stream().forEach(System.out::println);

The same is true for your single line statement. It has been my experience that IntelliJ is more flexible in how its auto formatting is applied. IntelliJ is less likely to remove or add line returns, if you put it there then it assumes you meant to put it there. IntelliJ will happily adjust your tab-space for you.

---

IntelliJ can also be configured to do some of this for you. Under "settings" -> "code style" -> "java", in the "Wrapping and Braces" tab you can set "chain method calls" to "wrap always".

Before Auto-Formatting

// Mulit-Line Statement
List<String> strings = Arrays.stream(ppl).filter((x) -> { return x.contains("(M)"); }).collect(Collectors.toList());

// Single-Line Statement
List<String> strings = Arrays.stream(ppl).map((x) -> x.toUpperCase()).filter((x) -> x.contains("(M)")).collect(Collectors.toList());

After Auto-Formatting

// Mulit-Line Statement
List<String> strings = Arrays.stream(ppl)
        .filter((x) -> {
            return x.contains("(M)");
        })
        .collect(Collectors.toList());

// Single-Line Statement
List<String> strings = Arrays.stream(ppl)
        .map((x) -> x.toUpperCase())
        .filter((x) -> x.contains("(M)"))
        .collect(Collectors.toList());