https://github.com/google/guava/guava: Guava is a suite of core and expanded libraries that include utility classes, google's collections, io classes, and much much more. 
final class com.google.common.collect.CollectPreconditions
  minor version: 0
  major version: 59
  flags: flags: (0x0030) ACC_FINAL, ACC_SUPER
  this_class: com.google.common.collect.CollectPreconditions
  super_class: java.lang.Object
{
  void <init>();
    descriptor: ()V
    flags: (0x0000) 
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // com.google.common.collect.CollectPreconditions this
         0: .line 26
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // com.google.common.collect.CollectPreconditions this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/collect/CollectPreconditions;

  static void checkEntryNotNull(java.lang.Object, java.lang.Object);
    descriptor: (Ljava/lang/Object;Ljava/lang/Object;)V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=5, locals=2, args_size=2
        start local 0 // java.lang.Object key
        start local 1 // java.lang.Object value
         0: .line 29
            aload 0 /* key */
            ifnonnull 2
         1: .line 30
            new java.lang.NullPointerException
            dup
            new java.lang.StringBuilder
            dup
            ldc "null key in entry: null="
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            aload 1 /* value */
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            invokespecial java.lang.NullPointerException.<init>:(Ljava/lang/String;)V
            athrow
         2: .line 31
      StackMap locals:
      StackMap stack:
            aload 1 /* value */
            ifnonnull 4
         3: .line 32
            new java.lang.NullPointerException
            dup
            new java.lang.StringBuilder
            dup
            ldc "null value in entry: "
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            aload 0 /* key */
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
            ldc "=null"
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            invokespecial java.lang.NullPointerException.<init>:(Ljava/lang/String;)V
            athrow
         4: .line 34
      StackMap locals:
      StackMap stack:
            return
        end local 1 // java.lang.Object value
        end local 0 // java.lang.Object key
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0    5     0    key  Ljava/lang/Object;
            0    5     1  value  Ljava/lang/Object;
    MethodParameters:
       Name  Flags
      key    
      value  

  static int checkNonnegative(int, java.lang.String);
    descriptor: (ILjava/lang/String;)I
    flags: (0x0008) ACC_STATIC
    Code:
      stack=5, locals=2, args_size=2
        start local 0 // int value
        start local 1 // java.lang.String name
         0: .line 38
            iload 0 /* value */
            ifge 2
         1: .line 39
            new java.lang.IllegalArgumentException
            dup
            new java.lang.StringBuilder
            dup
            aload 1 /* name */
            invokestatic java.lang.String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            ldc " cannot be negative but was: "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            iload 0 /* value */
            invokevirtual java.lang.StringBuilder.append:(I)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            invokespecial java.lang.IllegalArgumentException.<init>:(Ljava/lang/String;)V
            athrow
         2: .line 41
      StackMap locals:
      StackMap stack:
            iload 0 /* value */
            ireturn
        end local 1 // java.lang.String name
        end local 0 // int value
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0    3     0  value  I
            0    3     1   name  Ljava/lang/String;
    RuntimeInvisibleAnnotations: 
      com.google.errorprone.annotations.CanIgnoreReturnValue()
    MethodParameters:
       Name  Flags
      value  
      name   

  static long checkNonnegative(long, java.lang.String);
    descriptor: (JLjava/lang/String;)J
    flags: (0x0008) ACC_STATIC
    Code:
      stack=5, locals=3, args_size=2
        start local 0 // long value
        start local 2 // java.lang.String name
         0: .line 46
            lload 0 /* value */
            lconst_0
            lcmp
            ifge 2
         1: .line 47
            new java.lang.IllegalArgumentException
            dup
            new java.lang.StringBuilder
            dup
            aload 2 /* name */
            invokestatic java.lang.String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            ldc " cannot be negative but was: "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            lload 0 /* value */
            invokevirtual java.lang.StringBuilder.append:(J)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            invokespecial java.lang.IllegalArgumentException.<init>:(Ljava/lang/String;)V
            athrow
         2: .line 49
      StackMap locals:
      StackMap stack:
            lload 0 /* value */
            lreturn
        end local 2 // java.lang.String name
        end local 0 // long value
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0    3     0  value  J
            0    3     2   name  Ljava/lang/String;
    RuntimeInvisibleAnnotations: 
      com.google.errorprone.annotations.CanIgnoreReturnValue()
    MethodParameters:
       Name  Flags
      value  
      name   

  static void checkPositive(int, java.lang.String);
    descriptor: (ILjava/lang/String;)V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=5, locals=2, args_size=2
        start local 0 // int value
        start local 1 // java.lang.String name
         0: .line 53
            iload 0 /* value */
            ifgt 2
         1: .line 54
            new java.lang.IllegalArgumentException
            dup
            new java.lang.StringBuilder
            dup
            aload 1 /* name */
            invokestatic java.lang.String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            ldc " must be positive but was: "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            iload 0 /* value */
            invokevirtual java.lang.StringBuilder.append:(I)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            invokespecial java.lang.IllegalArgumentException.<init>:(Ljava/lang/String;)V
            athrow
         2: .line 56
      StackMap locals:
      StackMap stack:
            return
        end local 1 // java.lang.String name
        end local 0 // int value
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0    3     0  value  I
            0    3     1   name  Ljava/lang/String;
    MethodParameters:
       Name  Flags
      value  
      name   

  static void checkRemove(boolean);
    descriptor: (Z)V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // boolean canRemove
         0: .line 63
            iload 0 /* canRemove */
            ldc "no calls to next() since the last call to remove()"
            invokestatic com.google.common.base.Preconditions.checkState:(ZLjava/lang/Object;)V
         1: .line 64
            return
        end local 0 // boolean canRemove
      LocalVariableTable:
        Start  End  Slot       Name  Signature
            0    2     0  canRemove  Z
    MethodParameters:
           Name  Flags
      canRemove  
}
SourceFile: "CollectPreconditions.java"
    RuntimeInvisibleAnnotations: 
      com.google.common.annotations.GwtCompatible()