[platform] adds comparison methods to Java version class

platform/util/src/com/intellij/util/lang/JavaVersion.java

@@ -19,7 +19,7 @@ import java.util.List;
  * @see #parse(String) for examples of supported version strings
  * @since 2018.1
  */
-public final class JavaVersion {
+public final class JavaVersion implements Comparable<JavaVersion> {
   /**
    * The major version.
    * Corresponds to the first number of a Java 9+ version string and to the second number of Java 1.0 to 1.8 strings.
@@ -58,6 +58,23 @@ public final class JavaVersion {
     this.ea = ea;
   }
 
+  @Override
+  public int compareTo(@NotNull JavaVersion o) {
+    int diff = feature - o.feature;
+    if (diff != 0) return diff;
+    diff = minor - o.minor;
+    if (diff != 0) return diff;
+    diff = update - o.update;
+    if (diff != 0) return diff;
+    diff = build - o.build;
+    if (diff != 0) return diff;
+    return (ea ? 0 : 1) - (o.ea ? 0 : 1);
+  }
+
+  public boolean isAtLeast(int feature) {
+    return this.feature >= feature;
+  }
+
   @Override
   public boolean equals(Object o) {
     if (this == o) return true;

platform/util/testSrc/com/intellij/util/lang/JavaVersionTest.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+ * Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
  */
 package com.intellij.util.lang
 
@@ -60,6 +60,14 @@ class JavaVersionTest {
     assertThat(current.build).isGreaterThan(0)
   }
 
+  @Test fun comparing() {
+    assertThat(JavaVersion.compose(9, 0, 0, 0, false)).isGreaterThan(JavaVersion.compose(8, 0, 0, 0, false))
+    assertThat(JavaVersion.compose(8, 1, 0, 0, false)).isGreaterThan(JavaVersion.compose(8, 0, 0, 0, false))
+    assertThat(JavaVersion.compose(8, 0, 1, 0, false)).isGreaterThan(JavaVersion.compose(8, 0, 0, 0, false))
+    assertThat(JavaVersion.compose(8, 0, 0, 1, false)).isGreaterThan(JavaVersion.compose(8, 0, 0, 0, false))
+    assertThat(JavaVersion.compose(8, 0, 0, 0, false)).isGreaterThan(JavaVersion.compose(8, 0, 0, 0, true))
+  }
+
   private fun doTest(versionString: String,
                      feature: Int,
                      minor: Int = 0,