Unify method visibility of private classes

Apply checkstyle rule to ensure that private and package private
classes do not have unnecessary public methods. Test classes have
also been unified as much as possible to use default scoped
inner-classes.

Closes gh-7316

spring-boot-project/spring-boot-tools/spring-boot-configuration-docs/src/main/java/org/springframework/boot/configurationdocs/AsciidocBuilder.java

@@ -29,22 +29,22 @@ class AsciidocBuilder {
 		this.content = new StringBuilder();
 	}
 
-	public AsciidocBuilder appendKey(Object... items) {
+	AsciidocBuilder appendKey(Object... items) {
 		for (Object item : items) {
 			appendln("`+", item, "+` +");
 		}
 		return this;
 	}
 
-	public AsciidocBuilder newLine() {
+	AsciidocBuilder newLine() {
 		return append(System.lineSeparator());
 	}
 
-	public AsciidocBuilder appendln(Object... items) {
+	AsciidocBuilder appendln(Object... items) {
 		return append(items).newLine();
 	}
 
-	public AsciidocBuilder append(Object... items) {
+	AsciidocBuilder append(Object... items) {
 		for (Object item : items) {
 			this.content.append(item);
 		}

spring-boot-project/spring-boot-tools/spring-boot-configuration-docs/src/main/java/org/springframework/boot/configurationdocs/CompoundConfigurationTableEntry.java

@@ -44,7 +44,7 @@ class CompoundConfigurationTableEntry extends ConfigurationTableEntry {
 	}
 
 	@Override
-	public void write(AsciidocBuilder builder) {
+	void write(AsciidocBuilder builder) {
 		builder.append("|");
 		this.configurationKeys.forEach(builder::appendKey);
 		builder.newLine().appendln("|").appendln("|+++", this.description, "+++");

spring-boot-project/spring-boot-tools/spring-boot-configuration-docs/src/main/java/org/springframework/boot/configurationdocs/ConfigurationTable.java

@@ -36,7 +36,7 @@ class ConfigurationTable {
 		this.entries = new TreeSet<>();
 	}
 
-	public String getId() {
+	String getId() {
 		return this.id;
 	}
 

spring-boot-project/spring-boot-tools/spring-boot-configuration-docs/src/main/java/org/springframework/boot/configurationdocs/ConfigurationTableEntry.java

@@ -25,11 +25,11 @@ abstract class ConfigurationTableEntry implements Comparable<ConfigurationTableE
 
 	protected String key;
 
-	public String getKey() {
+	String getKey() {
 		return this.key;
 	}
 
-	public abstract void write(AsciidocBuilder builder);
+	abstract void write(AsciidocBuilder builder);
 
 	@Override
 	public boolean equals(Object obj) {

spring-boot-project/spring-boot-tools/spring-boot-configuration-docs/src/main/java/org/springframework/boot/configurationdocs/SingleConfigurationTableEntry.java

@@ -53,7 +53,7 @@ class SingleConfigurationTableEntry extends ConfigurationTableEntry {
 	}
 
 	@Override
-	public void write(AsciidocBuilder builder) {
+	void write(AsciidocBuilder builder) {
 		builder.appendln("|`+", this.key, "+`");
 		writeDefaultValue(builder);
 		writeDescription(builder);